The Internal Revenue Service includes a clergy housing allowance calculation form as part of "Worksheet 1. Figuring the Percentage of Tax-Free Income" at the end of publication 517, available at IRS.gov. Lines 1 to 6 cover all clergy housing allowance exclusions.
The U.S. tax code allows for members of the clergy to exclude a housing allowance from their gross income under certain circumstances, according to the IRS in 2015. The housing allowance can only be excluded if it is explicitly designated as a housing allowance before payment is made. Only the amount of the allowance that is actually used to provide for or rent a home may be excluded.