Generally, your taxes change due to a change in the tax tables.
Tax tables are set into law by the United States Congress and administered by the IRS. Each year, the new tables are posted on the IRS website in IRS Publication 15 and Notice 1036.
OPM is required by law to update your Federal income tax withholding based on the new monthly periodic tax tables and formulas. OPM withholds the required federal taxes according to your marital status and exemptions (dependents) elected. You can change your tax withholding amount at any time. It is a good idea to check the amount of your Federal and State tax withholding each year.
There was an unexpected error when performing your action.
Your error has been logged and the appropriate people notified. You may close this message and try your command again, perhaps after refreshing the page. If you continue to experience issues, please notify the site administrator.