26 C.F.R. § 31.3121(i)-4
In any case where an individual is a member of a religious order (as defined in section 3121(r)(2) and paragraph (b) of § 31.3121(r)-1 ) performing service in the exercise of duties required by such order, and an election of coverage under section 3121(r) and § 31.3121(r)-1 is in effect with respect to such order or the autonomous subdivision thereof to which such member belongs, the term "wages" shall, subject to the provisions of section 3121(a)(1) (relating to definition of wages), include as such individual's remuneration for such service the fair market value of any board, lodging, clothing, and other perquisites furnished to such member by such order or subdivision or by any other person or organization pursuant to an agreement (whether written or oral) with such order or subdivision. Such other perquisites shall include any cash either paid by such order or subdivision or paid by another employer and not required by such order or subdivision to be remitted to it. For purposes of this section, perquisites shall be considered to be furnished over the period during which the member receives the benefit of them. (See example 4 of this section.) In no case shall the amount included as such individual's remuneration under this paragraph be less than $100 a month. All relevant facts and elements of value shall be considered in every case. Where the fair market value of any board, lodging, clothing, and other perquisites furnished to all members of an electing religious order or autonomous subdivision (or to all in a group of members) does not vary significantly, such order or subdivision may treat all of its members (or all in such group of members) as having a uniform wage. The provisions of this section may be illustrated by the following examples of the treatment of particular perquisites:
Example 1. M is a religious order which requires its members to take a vow of poverty and which has made an election under section 3121(r). Under section 3121(i)(4), M must include in the wages of its members the fair market value of the clothing it provides for its members. M and several other religious orders using essentially the same type of religious habit purchase clothing for their members from either of two suppliers in arms-length transactions. The fair market value of such clothing (i.e., the price at which such items would change hands between a willing buyer and a willing seller, neither being under any compulsion to buy or to sell) is determined by reference to the actual sales price of these suppliers to the religious orders.
Example 2. N is a religious order which requires its members to take a vow of poverty and which has made an election under section 3121(r). N operates a seminary adjacent to a university. Students at the university obtain lodging and board on campus from the university for its fair market value of $2,000 for the school year. Such lodging and board is essentially the same as that provided by N at its seminary to N's members subject to a vow of poverty. Accordingly, the amount to be included in the "wages" of such members with respect to lodging and board for the same period of time is $2,000.
Example 3. O is a religious order which requires its members to take a vow of poverty and to observe silence, and which has made an election under section 3121(r). O operates a monastery in a remote rural area. Under section 3121(i)(4), O must include in the wages of its members assigned to this monastery the fair market value of the board and lodging furnished to them. In making a determination of the fair market value of such board and lodging, the remoteness of the monastery, as well as the smallness of the rooms and the simplicity of their furnishings, affect this determination. However, the facts that the facility is used by a religious order as a monastery and that the order's members maintain silence do not affect the fair market value of such items.
Example 4. P is a religious order which requires its members to take a vow of poverty and which has made an election under section 3121(r). Several of P's members are attending a university on a full-time basis. The fair market value of the board and lodging of each of such members at the university is $1,000 per semester. P pays the university $1,000 at the beginning of each semester for the board and lodging of each of such members. In addition, P gives each such member a $400 cash advance to cover his miscellaneous expenses during the semester. Under section 3121(i)(4), P must prorate the fair market value of such members' board and lodging, as well as the miscellaneous items, over the semester and include such value in the determination of "wages".
Example 5. Q is a religious order which is a corporation organized under the laws of Wisconsin, which requires its members to take a vow of poverty, and which has made an election under section 3121(r). Q has convents in rural South America and in suburbs and central city areas of the United States. Characteristically, in the United States its suburban convents provide somewhat larger and newer rooms for its members than do its convents in city areas. Moreover, its suburban convents have more extensive grounds and somewhat more elaborate facilities than do its older convents in city areas. However, both types of convents limit resident members to a single, plainly furnished room and provide them meals which are comparable. Q's members in South America live in extremely primitive dwellings and otherwise have extremely modest perquisites. Under section 3121(i)(4), Q may report a uniform wage for its members who live in suburban convents and city convents in the United States, as the board, lodging, and perquisites furnished these members do not vary significantly from one convent to the other. Q may report another uniform wage (but not less than $100 per month apiece) for its members who are citizens of the United States and who reside in South America based on the fair market value of the perquisites furnished these individuals, as the fair market value of the perquisites furnished these individuals varies significantly from that of those furnished its members who live in its domestic convents but does not vary significantly among members in South America whose wages are subject to tax.
26 C.F.R. §31.3121(i)-4