Quick search by citation:

5 U.S. Code § 10209 - Clothing allowances

(a) In General.—
In addition to the benefits provided under section 5901, the Director of the United States Secret Service or the designee of the Director is authorized to provide a clothing allowance to a member assigned to perform duties in normal business or work attire purchased at the discretion of the employee. Such clothing allowance shall not to be treated as part of the member’s basic pay for any purpose (including retirement purposes) and shall not be used for the purpose of computing the member’s overtime pay, pay during leave or other paid time off, lump-sum payments under section 5551 or section 5552, workers’ compensation, or any other benefit. Such allowance for any member may be discontinued at any time upon written notification by the Director of the United States Secret Service or the designee of the Director.
(b) Maximum Amount Authorized.—
A clothing allowance authorized under this section shall not exceed $500 per annum.
Statutory Notes and Related Subsidiaries
Effective Date

Section effective on first day of first pay period which begins after Oct. 15, 2010, see section 5 of Pub. L. 111–282, set out as an Effective Date of 2010 Amendment note under section 5102 of this title.