DYKMAN, J.
The individual plaintiffs in this action are members of a monastic community of Roman Catholic women known as a priory. The sisters make their facilities1 available to individuals and groups for re[538]*538treats or for use as a meeting place. The issue they raise is whether the fee which they charge for meals served to those who visit the premises is subject to Wisconsin’s sales tax. In order to decide this issue, we must determine whether the sales tax applies to the sisters’ sale of meals, and if so, whether this taxation violates their constitutional right to the free exercise of their religion.
The following facts are taken from the testimony given at a hearing held in Dane County Circuit Court on March 28 and 29, 1978, and from the exhibits which were introduced into evidence at that hearing. The department of revenue (department) made no attempt to contradict or impeach the vast majority of the evidence presented by the sisters at that hearing. Thus, the facts are largely undisputed.
The priory is incorporated under the name “Sisters of St. Benedict of Madison, Wisconsin.” The priory is a part of the Federation of St. Gertrude, which in turn is a part of the Benedictine Order.2 Members of the priory [539]*539follow the Rule of St. Benedict. While this rule has many facets, the portion which is of primary significance to this action is chapter 53, “On the Reception of Guests,” which begins, “Let all guests who arrive be received like Christ, for He is going to say, T came as a guest, and you received Me.’ ”3
The Benedictine communities which comprise the Federation of St. Gertrude engage in activities which they believe are appropriate for the time and their location. As times change and the communities relocate or expand, the work which the sisters do changes accordingly. When the sisters first arrived in Madison,4 they came in re[540]*540sponse to a call from a bishop to staff a parochial girl’s school. The school began its operation in 1959, but over the years it experienced difficulty in attracting students.
During the mid-sixties, the sisters began offering weekend retreats.5 In 1966, the Executive Committee of the Madison Interfaith Dialogue, a group of clergymen working to advance the spirit of ecumenism in the Madison area, requested that retreats be offered on a broader basis. The bishop approved this request. The sisters ultimately decided that their ability to provide retreats and a central gathering place for those interested in furthering ecumenism was of greater worth to the community than was their school. They closed the school, named their facilities “St. Benedict Center,” and began to develop retreats and conferences consistent with their purpose of furthering an ecumenical dialogue within the city. They also believed that the reception of guests at the center was consistent with chapter 53 of the Rule of St. Benedict.
The sisters and members of the center’s advisory board were concerned that the activities of the center would be focused too narrowly. The sisters and others active in the center’s work wanted to carry on a continuing dialogue with as much of the community as possible. They [541]*541did not want to limit access to the center solely to religious leaders and church groups. Toward the end of broadening the base of people who made use of the center, the sisters sent letters to businesses offering the use of the center as a meeting place.6
The center has been used as a meeting place by government agencies, university groups, church groups, nonprofit organizations, and business groups. The center provides several meeting rooms, including a large auditorium for these groups to use. It also offers outdoor recreational opportunities. The center provides overnight use of the facilities for a fixed fee,7 including a room, linens, three meals, two coffee breaks, and facility use. It also provides, again for a fixed fee, daytime facility use, including lunch and coffee breaks, and evening facility use, including dinner and one coffee break. In addition, the center makes equipment such as projectors and typewriters available for a rental fee.
Effective September 1, 1977, the base rate for an overnight stay was $22.50 per person, or $40 per couple. For church related groups, however, these rates were discounted to $19 per person and $34 per couple. Daytime and evening rates were $6 and $5.50 per person, respectively. No discounts were offered to church groups for daytime and evening rates.
The food which the sisters prepare is simple, and normally includes vegetables grown in the center’s garden. There is no menu. The rooms provided for overnight stay are also simple. Guests are expected to make up their own beds when they arrive.
[542]*542In accordance with the Rule of St. Benedict, if a guest arrives who cannot afford to pay for food or lodging, he is not turned away. The guest is asked to do some work around the center in exchange for the sisters’ hospitality. Even those guests who pay are invited to help with the dishes.
Guests at the center are given a short orientation lecture and are invited to attend the daily prayer meetings if they wish to do so. The sisters join the guests at their meals and converse with them. They do not discuss religion during their meals with business guests unless the guests bring it up.
The sisters’ attorney received a letter dated January 10, 1974, from a representative of the department which stated that it would be necessary to have St. Benedict Center register for sales tax, obtain a permit, and make records for sale of meals available from September 1, 1969 to date. He also received a letter dated February 8, 1974, stating that the sisters fell within the definition of “retailer” provided in sec. 77.51(7) (a), Stats., and that the gross receipts from their sale of meals were subject to taxation.8 Section 77.52(12), Stats., provides that any person who operates as a seller in the State of Wisconsin without a permit is guilty of a misdemeanor.
The sisters brought this action for a declaratory judgment, claiming that the state’s threat to impose a sales tax on them violates their right to the free exercise of their religion, contrary to both the state9 and federal10 [543]*543constitutions,11 and to 42 U.S.C. sec. 1983.12 The sisters also asked that the department be enjoined from attempting to penalize them for failure to obtain a sales tax permit and from requiring them to pay a tax on their sales. In its answer, the department requested a judgment declaring that the sisters are required to obtain a sales tax permit for the sale of meals, and to pay tax on non-exempt sales.
Two issues are raised for our consideration on appeal:
(1) Does the sales tax apply to the sisters’ sale of meals to business groups ?
(2) If the sales tax does so apply, does imposition of liability for collection of the sales tax on the sisters violate their right to the free exercise of their religion?
(1) Applicability of Sales Tax
The sisters first contend that the sales tax statutes do not apply to their sale of meals to business groups.13 [544]*544The department relies on sec. 77.52(1), Stats., to establish its taxing authority. That statute provides in part: “For the privilege of selling . . . tangible personal property ... at retail a tax is hereby imposed on all retailers . . . .” Tangible personal property is defined broadly as “all tangible personal property of every kind and description.” Sec. 77.51 (5).
The sisters argue, however, that they are not retailers, and that the tax thus does not apply to them. The term “retailer” is defined by statute as follows: “ ‘Retailer’ includes: (a) Every seller who makes any sale of tangible personal property or taxable service.” (Emphasis added.) Sec. 77.51(7) (a), Stats. The terms “sale” and “seller” are given these definitions:
“Sale”, “sale, lease or rental”, “retail sale”, “sale at retail”, or equivalent terms include any one or all of the following: . . .
(f) The furnishing, preparing or serving for consideration of food, meals, confections or drinks. Sec. 77.51 (4), Stats.
“Seller” includes every person selling . . . tangible personal property or selling ... or furnishing services of a kind the gross receipts from the sale ... of which are required to be included in the measure of the sales tax. Sec. 77.51 (9), Stats.
Section 77.54(20) (c)l, Stats., provides that “[t]he gross receipts from sales of meals, food, food products and beverages sold by any person, organization or establishment for direct consumption on the premises are taxable
Thus, in furnishing meals for consideration, the sisters are making sales. Sec. 77.51 (4), Stats. Because the gross receipts from the sale of the meals are subject to taxation, sec. 77.54 (20) (c) 1, the sisters are a seller. Sec. [545]*54577.51(9). Because the sisters are a seller making* sales of tangible personal property, they are a retailer, sec. 77.-51(7) (a), and are accordingly subject to taxation by virtue of sec. 77.52.(1).
The sisters, however, point to a different definition of “retailer” to suggest that they are not covered by the sales tax statutes. Section 77.51(7) (b), Stats., provides that “retailer” includes a person “engaged in the business of making sales of tangible personal property.” The sisters claim that they are not engaged in a business, since they are not engaged in an activity “with the object of gain, benefit or advantage.” Sec. 77.51 (8).
The sisters argue that this definition of retailer is applicable rather than the definition provided in sec. 77.51 (7) (a), Stats., because the latter definition is meaningless. They reason: In order to be a retailer under sec. 77.-51 (7) (a), it is necessary to be a seller. In order to be a seller under sec. 77.51(9), one must sell something, the gross receipts of which are required to be included in the measure of the sales tax. But the receipts are only required to be included in the measure of the sales tax, the sisters assert, if the seller is a retailer under sec. 77.52 (1). They conclude that these statutes revolve on a perpetual track, and are ultimately meaningless.
This logic does not take into account sec. 77.54(20) (c)l, Stats., which expressly provides that the sale of meals is subject to the sales tax. Thus, the sisters are a seller under sec. 77.51(9), Stats., not because they are a retailer, but because they are selling meals, the gross receipts from which are expressly required to be taxed. Accordingly, the sisters fit within the definition of retailer found in sec. 77.51(7) (a), even if they are not retailers within the meaning of sec. 77.51(7) (b).
The sisters next contend that they are exempt from the sales tax because they make only occasional sales. An occasional sale is defined by sec. 77.51(10), Stats.:
[546]*546(a) Isolated and sporadic sales of tangible personal property or taxable services where the infrequency, in relation to the other circumstances, including the sales price and the gross profit, support the inference that the seller is not pursuing a vocation, occupation or business or a partial vocation or occupation or part-time business as a vendor of personal property or taxable services. . . .
(c) Sales of admissions or tickets by a . . . church . . . or similar organization to an event, including a meal, not involving professional entertainment, conducted by such organization, when such organization is not engaged in a trade or business and not otherwise required to have a seller’s permit, and when no more than 3 such events were conducted by the organization in the previous calendar year and no more than 3 are anticipated during the current calendar year and such events do not fall on more than 7 different days within the calendar year.
The occasional sales of tangible personal property and services are exempt from sales tax. Sec. 77.54(7), Stats.
The sisters do not dispute that they sold meals on more than three occasions per year. They suggest two reasons, however, why sec. 77.51(10) (c), Stats., should not be seen as a limitation on the sec. 77.51(10) (a) definition of occasional sales. The first of these is that sec. 77.51 (10) (a) should be read together with the definition of retailer found in sec. 77.51(7) (b), to establish the legislative purpose of taxing only business sales. Accordingly, sec. 77.51(10) (c) should come into play only when the person claiming exemption is engaged in a business. This argument is unsupported by either logic or authority. The three-event rule is a specific legislative definition of what should and should not be considered an occasional sale. Further, the statute by its terms applies only to organizations which are not engaged in a business.
The second contention is that sec. 77.51 (10) (c), Stats., applies only to admissions, and that the three-event rule [547]*547thus pertains only to amusement or entertainment events. While the statute does use the term admissions, it also refers specifically to the sale of admissions “to an event, including a meal.” This language indicates that the three-event rule was intended to apply to the sale of meals.
Because the sisters have been operating as a retailer within the meaning of the statute, and because their sales are not exempt as occasional sales, we conclude that the statutes required them to obtain a sales tax permit and pay tax on non-exempt sales of meals.
(2) Free Exercise of Religion
The sisters contend that requiring them to comply with the sales tax statutes infringes on their constitutional right to the free exercise of their religion. They presented substantial evidence at trial to prove that all of the work which they do is religiously, rather than commercially, motivated. Their evidence indicated that their reception of guests is consistent with the Rule of St. Benedict; hospitality toward visitors is an important part of that rule. They also presented evidence to show that they viewed eating with the guests at meals to be a religious activity. This is true in part because providing meals to guests and joining them while they eat promotes the ecumenical dialogue which they seek to establish, and in part because the meal itself is traditionally seen as a religious activity.14 Because they see the serving of [548]*548meals as an exercise of their religious beliefs, they urge us to hold that taxation of the sale of those meals is taxation of religion, in violation of the freedom of religion guarantees of the state and federal constitutions.
In ruling on this issue, the trial judge made the following findings of fact:
(1) None of the work performed by the plaintiff Sisters is done for profit.
(2) Members of business groups and other non-religious groups who eat meals purchased at the center are not involved in any religious activities of the plaintiffs.
(3) The record is barren of evidence that any religious dialogue took place at meals between the Sisters and business or other non-religious guests.
(4) The Center operated at a net loss during each of the years 1973 through 1977.
(5) The plaintiff corporation was organized exclusively for religious and charitable purposes.
(6) A number of business groups and other persons not exempt from the sales tax have eaten and paid for meals at the Center.
(7) Church and religious-related groups are charged less for meals than are business groups and other nonexempt users.
(8) During the years 1971 through 1974 the Center actively solicited patronage from Madison area business and industrial groups without making any reference to religion or the exercise thereof.
(12) The sales of the meals in question to business and other non-exempt groups are not related to religion, and there is no probative evidence that they were so related.
[549]*549(IB) The plaintiff Sisters were engaged in a business rather than a religious exercise in furnishing and selling meals to business and other non-exempt groups at rates higher than those charged religiously related groups.
The basis for the last finding is explained in the court’s memorandum decision. The court noted that the sisters had solicited inquiries about the use of the center by members of the business community, “probably in order to keep the center viable and flourishing.” The court also found that the sisters’ discount of their rates for church-related groups was an indication that they were not pursuing an exercise of their religion when they served meals to business groups. For these reasons, the court concluded that the sale of meals to business groups was a commercial activity, and that subjecting that activity to sales taxation did not violate the sisters’ free exercise rights.
When a trial court acts as the finder of fact, we will sustain its findings unless they are against the great weight and clear preponderance of the evidence. “Also when more than one reasonable inference can be drawn from the evidence, this court is obliged to support the finding made by the trial court.” Onalaska Electrical Heating, Inc. v. Schaller, 94 Wis.2d 493, 501, 288 N.W.2d 829, 883 (1980).15
[550]*550The Wisconsin Supreme Court has recognized that “[n]o liberty guaranteed by our constitution is more important or vital to our free society than is a religious liberty protected by the free exercise clause of the first amendment.” State v. Yoder, 49 Wis.2d 430, 434, 182 N.W.2d 539, 540 (1971), aff’d sub nom., Wisconsin v. Yoder, 406 U.S. 205 (1972). Accordingly, the test for determining whether the state is violating the free exercise of religion is strict. To withstand a free exercise challenge, there must be either no infringement by the state on free exercise, or if free exercise is burdened, the burden must be justified by a “compelling state interest in the regulation of a subject within the State’s constitutional power to regulate.” Sherbert v. Verner, 374 U.S. 398, 403 (1963) quoting NAACP v. Button, 371 U.S. 415 (1963). Even if the burden is “incidental,” this test must be met. Sherbert, 374 U.S. at 403. “No mere showing of a rational relationship to some colorable state interest will suffice; in the highly sensitive area of religious freedom, only the gravest abuses endangering paramount interests justify state intrusion.” State v. Kasuboski, 87 Wis.2d 407, 416, 275 N.W.2d 101, 105 (Ct. App. 1978).
It is not sufficient, however, for a person challenging the application of a statute on free exercise grounds merely to show that the statute burdens him in some way. The burden must be related to the exercise of a religious belief.
The Free Exercise Clause . . . withdraws from legislative power, state and federal, the exertion of any restraint on the free exercise of religion. Its purpose is to secure religious liberty in the individual by prohibiting any invasions thereof by civil authority. Hence it is necessary in a free exercise case for one to show the coercive effect of the enactment as it operates against [551]*551him in the practice of his religion. Abington School District v. Schempp, 374 U.S. 203, 222-23 (1963).
We must therefore determine whether application of the sales tax to the sisters’ sale of meals has a coercive effect upon their exercise of religion.
The taxation of religion, or a tax laid specifically on the exercise of religion, is inherently unconstitutional as a coercive burden on the free exercise of religion. Murdock v. Pennsylvania, 319 U.S. 105, 108 (1943). The sisters suggest that the sales tax is, in effect, a tax on religion, and is accordingly violative of their right to freedom of religion.
In order to evaluate this contention, we bear in mind that there are present in this case two conflicting perspectives on whether the meals which the sisters serve and which the state seeks to tax are part of a religious activity. The testimony presented by and on behalf of the sisters indicates that inviting guests into the facilities, serving them meals, eating and interacting with them, and providing the opportunity for a dialogue, whether or not religious and whether or not it actually takes place, is a religious activity in accord with the Rule of St. Benedict and the sisters’ dedication to the principle of ecumenism. The sincerity of this belief has not been questioned, and the court may not evaluate the validity, reasonableness, or merits of the belief. Yoder, 49 Wis.2d at 436, 182 N.W.2d at 541-42. We must therefore accept as a given that the sisters are engaged in the exercise of religion when they serve meals to their guests and join them in dining.
From the perspective of the business guests of the center, however, the trial court found that partaking in meals was not a religious activity. Only one businessman testified that he had attended any prayer meetings at the center. The judge found the record as a whole [552]*552devoid of evidence that business groups felt that sharing the meals was a religious exercise. This formed part of the basis for the court’s conclusion that the meals which the sisters serve are not part of an exercise of religion.
It is the sisters, however, who seek exemption from taxation on religious grounds; not the businessmen. For the purpose of evaluating the sisters’ claim that imposing a sales tax on them violates their freedom of religion, the religious views of their guests are irrelevant. We must therefore accept as asserted that the sisters engage in religious activity when serving meals to guests and when eating with them.
Our next inquiry is whether the fact that the sisters charge for the meals as part of the fee for using the facilities transforms a religious activity into a commercial one. We conclude that it does not. The Supreme Court was faced with a similar question in Murdock, 319 U.S. 105. In that case, a city required a member of Jehovah’s Witnesses to pay a fee and obtain a license before he could sell religious books and tracts door to door. Justice Douglas, writing for the Court, first found that the distribution of religious literature was protected by the free exercise clause. He then addressed the issue of whether it was proper to exact the license tax as a condition of distributing the literature when the Jehovah’s Witness asked for money in exchange for the literature:
[T]he mere fact that the religious literature is “sold” by itinerant preachers rather than “donated” does not transform evangelism into a commercial enterprise. If it did, then the passing of the collection plate in church would make the church service a commercial project. The constitutional rights of those spreading their religious beliefs through the spoken and printed word are not to be gauged by standards governing retailers or wholesalers of books. ... It is plain that a religious organization needs funds to remain a going concern. But an itinerant evangelist, however misguided or intolerant he [553]*553may be, does not become a mere book agent by selling the Bible or religious tracts to help defray his expenses or to sustain him. Freedom of speech, freedom of the press, freedom of religion are available to all, not merely to those who can pay their own way. As we have said, the problem of drawing the line between a purely commercial activity and a religious one will at times be difficult. On this record it plainly cannot be said that petitioners were engaged in a commercial rather than a religious venture. It is a distortion of the facts of record to describe their activities as the occupation of selling books and pamphlets. (Emphasis added.) Murdock, 319 U.S. at 111.
In Follett v. McCormick, 321 U.S. 573 (1944), the Court made clear that its holding in Murdock was not limited to itinerant preachers who merely helped defray expenses by charging for the materials they distributed. In that case, the Court held that even when the seller was not itinerant and made his living by selling religious materials door to door, conditioning his right to sell the materials upon payment of a license tax violated his right to the free exercise of his religion.
By the same process of reasoning, we conclude that the sisters’ activities should not be considered “commercial” simply because they charge a fee for the meals. The trial court’s findings to the contrary are not supported by the great weight and clear preponderance of the evidence.
As we have noted, the sisters introduced a substantial amount of testimony to the effect that the reception of guests, and particularly eating meals with them, was purely a religious activity. That testimony was not contradicted by the state. The trial court’s finding that the sale of meals was commercial was based upon two inferences, neither of which is supported by the record.
The first of these inferences was that the sisters invited business groups to use the facilities in an attempt to generate income and keep the center running. The court [554]*554drew this inference from letters which the sisters sent to businesses to make them aware of the center’s existence. While the letters included a fee schedule, we do not agree with the court’s implicit conclusion that the letters, by including the schedule and failing to mention religion, give rise to an inference that the sisters were engaged in a commercial activity. The religious nature of the sisters’ activities was made clear to the business groups which responded to the letters. The inference that the sisters solicited groups for a commercial purpose is also inconsistent with the sisters’ testimony that they turned away groups which did not fit into their community.16 All of the evidence in the record which addresses this point indicates that the sisters invited büsiness groups into the center in order to expand their role in developing an ecumenical dialogue in the community; to interact with as many people as possible who might be interested in their activities.17 In light of the great deference we must give to persons or groups who sincerely believe that their activities are religious, we cannot conclude that the record supports a finding that the sisters engaged in a commercial activity.
The court’s second inference was that the discounted rates made available to church groups reflected a commercial purpose in inviting business groups to use the facilities. We do not believe that this inference is reasonable in light of the sisters’ testimony that a lower rate was charged to those groups solely because the payment of fees was thought to be more burdensome to nonprofit church groups than it would be to business [555]*555groups.18 The state made no attempt to contradict this explanation for the rate differential.
We conclude on the basis of the record as a whole that the sisters were at no time engaged in a commercial enterprise in furnishing meals to business groups. The uncontradicted evidence demonstrates that they were pursuing a purely religious purpose in so doing.
Given that the sisters were engaging in the free exercise of their religion in furnishing meals for a fee to business groups who used their facilities, we must determine whether the sales tax is a tax on their religious activities, or, if not, whether it is nonetheless a burden on the free exercise of their religion.
Not all taxation imposed on a religious group is inherently burdensome of free exercise rights. As the Court stated in Murdock, 319 U.S. at 112:
We do not mean to say that religious groups . . . are free from all financial burdens of government. We have here something quite different, for example, from a tax on the income of one who engages in religious activities or a tax on property used or employed in connection with those activities. It is one thing to impose a tax on the income or property of a preacher. It is quite another thing to exact a tax from him for the privilege of delivering a sermon. (Citation omitted.)
As the court stated in Muste v. Commissioner, 35 T.C. 913, 918 (1961) : “It is clear . . . that a taxing statute is not contrary to the provisions of the first amendment unless it directly restricts the free exercise by an individual of his religion.” Unless the tax is imposed as a condition on the right to exercise one’s religion, or unless [556]*556its imposition is a burden to free exercise, the tax does not violate the first amendment.19
In order to determine whether application of the sales tax to the sisters’ activities is constitutional, we must consider the nature of the sales tax. Unlike the license tax in Murdock, the sisters are not required to pay the tax as a condition of their exercise of religion.20 Although the sisters are liable for the tax if it is not paid to the state, the tax may be collected from the consumer. Sec. 77.52(3), Stats. We take judicial notice of the fact that most retailers, including establishments which prepare and sell meals, collect the sales tax from the consumer. Thus, the sisters are not being asked to pay a tax as a condition of the exercise of their religion. They are instead being asked to collect a tax from the consumer and pass it along to the state. This taxing scheme avoids the fears of the Court in Murdock, 319 U.S. 105; the state cannot easily use the tax to deter the sisters from exercising their religion.21 Thus, this is not a tax imposed directly on religion, and it does not violate the first [557]*557amendment unless it imposes a burden on the sisters’ free exercise of religion.
Our inquiry must shift, then, to whether imposition of sales tax liability from the sisters’ sale of meals, which they may discharge by collecting the tax from the consumers or by demonstrating that the consumer is an exempt purchaser,22 imposes an unconstitutional burden on their exercise of religion. On the record before us, we must hold that it does not.
Statutes are presumed to be constitutional. One who challenges the constitutionality of a statute has the burden of demonstrating its unconstitutionality beyond a reasonable doubt. We must indulge in every presumption to sustain the statute against an attack on its constitutionality. Wis. Bingo Sup. & Equip. Co. v. Bingo Control Bd., 88 Wis.2d 293, 301, 276 N.W.2d 716, 719 (1979).
The sisters have failed to put forth any evidence to indicate that requiring them to act as a collector of the sales tax would have a coercive impact on their religious beliefs, or that it would burden their free exercise of those beliefs. The only burden to the sisters which we envision is that they will be required to keep more complete bookkeeping records than those which they now have. This burden, if in fact it is a burden, would not infringe on the free exercise of their religion. The burden is no greater than that imposed by the requirement that a church withhold taxes from the salaries of its janitors and pianist and transmit them to the government, a requirement that has been sustained against a free exercise attack.23 We conclude that the sisters have [558]*558not overcome the presumption of constitutionality of the sales tax statutes by demonstrating that their exercise of religion would be burdened by complying with them.24
The sisters have also failed to demonstrate that their liability for uncollected sales tax to date will burden their exercise of religion. If the sisters had applied for a sales tax permit before they began to sell meals, and had collected the tax and forwarded it to the state, any burden they may have now would not have arisen. We cannot hold that the sisters could defeat the taxing statutes by failing to comply with them, thus creating a burden when their tax liability began to mount up, and using that burden as a means of arguing that the taxing statutes are unconstitutional as applied to their sale of meals. In the absence of any evidence of an actual burden, however, we need only hold that the sisters have failed to demonstrate that their liability for taxes accrued to this date burdens their free exercise of religion.
We conclude that, while the sisters are engaged in a religious activity in furnishing meals to their guests for consideration, the requirement that they collect a sales tax on the sale of those meals is neither a tax on religion nor a burden to their exercise of religion. Accordingly, we sustain the constitutionality of the statute as applied to the sisters.
By the Court. — Judgment affirmed.