41 CFR § 302-17.20
What is the purpose of the WTA?
June 9, 2020
The purpose of the WTA is to protect you from having to use part of your relocation expense reimbursements to pay Federal income tax withholding; it does not cover state taxes, local taxes, Medicare taxes, or Social Security taxes (see §302-17.22(c) and (d)).
Note to §302-17.20: If your agency offers you the choice, the WTA is optional to you. See §§302-17.61 through 302-17.69.