You are required to file withholding certificates when you begin employment with the City of New York or transfer to another agency. You may also file new forms whenever your tax situation changes; for instance:
We recommend that you review your withholding allowance every year because changes in tax law may affect your tax even if other factors remain constant.
City agencies keep your withholding certificates and any supporting documentation you provide in your personnel file. In some instances, such as filings for excessive allowances and full exemption, copies of the forms and documentation are sent to OPA, IRS and NYS Department of Taxation & Finance.
There may be valid reasons for changing your withholding allowances. If you submit four or more changes in a calendar year, copies of the forms and documentation will be sent to OPA, the IRS and NYS for review.
If the IRS determines that you do not have enough federal income tax withheld, they may issue a Lock-In Letter, which directs your employer to automatically increase your withholding tax regardless of the amount of withholdings you have requested.