You should follow the procedures prescribed for the relocation income tax allowance, see §§ 302-11.7, 302-11.8 and the appropriate RIT tax table(s) located at www.gsa.gov/ftrbulletin or as illustrated in § 301-11.535.
Code of Federal Regulations
[64 FR 32813, June 18, 1999, as amended by FTR Amdt. 2008-04, 73 FR 35953, June 25, 2008]