41 C.F.R. § 302-17.1
The following definitions apply to this part:
Allowance means:
City means any unit of general local government as defined in 31 CFR 215.2(b) .
Combined marginal tax rate (CMTR) means a single rate determined by combining the applicable marginal tax rates for Federal, state, and local income taxes, using the formula provided in § 302-17.40. (If you incur liability for income tax in the Commonwealth of Puerto Rico, see § 302-17.44.)
County means any unit of local general government as defined in 31 CFR 215.2(e) .
Gross-up used as a noun in this part means:
Note: The gross-up allows for the fact that every reimbursement of taxes is itself taxable. Therefore, the gross-up calculates the amount an agency must reimburse an employee to cover substantially all of the income taxes incurred as the result of a relocation.
Internal Revenue Code (IRC) means Title 26 of the United States Code, which governs Federal income taxes.
Local income tax means a tax imposed by a recognized city or county tax authority that is deductible for Federal income tax purposes as a local income tax under the IRC, at 26 U.S.C. 164(a)(3) . (See the definitions for the terms city and county in this section.)
Marginal tax rate (MTR) means the tax rate that applies to the last increment of taxable income after taxable relocation benefits have been added to the employee's income. Examples of how to determine the marginal tax rate using the IRS Tax Rate Schedules are published in an FTR bulletin at https://gsa.gov/ftrbulletins.
Reimbursement means money paid to you to cover expenses that you have already paid for out of your own funds.
Relocation benefits means all reimbursements and allowances that you receive, plus all direct payments that your agency makes on your behalf, in connection with your relocation.
Relocation income tax allowance (RITA) means the payment to individuals to cover the difference between the withholding tax allowance (WTA), if any, and the actual income tax liability incurred by the individual, and such individual's spouse (if filing jointly), as a result of their taxable relocation benefits authorized pursuant to this chapter. RITA is paid whenever the actual income tax liability exceeds the WTA and applies to any travel, transportation, and relocation expenses reimbursed or furnished in kind pursuant to chapter 57, subchapter II of title 5 U.S.C. and 5 U.S.C. chapter 41.
State means any one of the several states of the United States, the District of Columbia, the Commonwealth of Puerto Rico, the Commonwealth of the Northern Mariana Islands, or any other territory or possession of the United States.
State income tax means a tax imposed by a state tax authority that is deductible for Federal income tax purposes under the IRC, specifically 26 U.S.C. 164(a)(3) .
Withholding tax allowance (WTA) means the amount paid to the Federal IRS by the agency as withholding of income taxes for any taxable relocation allowance, reimbursement, or direct payment to a vendor.
41 C.F.R. §302-17.1