To change the federal tax withheld from your civil service annuity, complete IRS Form W-4P and submit it to the Office of Personnel Management online through Retirement Services Online, by phone, or by mail. The OPM tax withholding Form W-4P lets you tell OPM your filing status and any adjustments so the right amount comes out of each monthly payment. If you never submit one, OPM withholds at the default rate: single filing status with no adjustments, which often pulls more than a married or lower-income retiree actually owes.
What to Have Ready
You need your CSA or CSF claim number before you do anything else. It starts with “CSA” (Civil Service Annuitant) or “CSF” (Civil Service Survivor) followed by digits and a suffix character, and OPM uses it to identify your account on every channel. A form or call without it risks being lost or delayed.
Pull your most recent tax return so you can estimate this year’s liability. If you have income OPM doesn’t see, such as Social Security, a part-time job, or investment income, have those figures too. The IRS Tax Withholding Estimator at irs.gov/W4App will calculate a target withholding number for you before you fill anything out.
Filling Out Form W-4P
Form W-4P is the IRS withholding certificate for periodic pension and annuity payments. It no longer uses “allowances”; the inputs are your filing status and actual dollar adjustments. You can download the PDF from the IRS or complete the equivalent inputs directly in OPM’s online portal without handling a paper form.
Step 1: Filing Status
Pick one: single or married filing separately, married filing jointly or qualifying surviving spouse, or head of household. This sets the tax brackets OPM applies. Match it to the status you actually plan to file under, because a mismatch here distorts every dollar calculated below it.
Step 2: Other Income in the Household
If your household has more than one income stream, such as a spouse’s wages, a second pension, or your own part-time work, Step 2 prevents under-withholding by accounting for the total. You can either use the IRS Tax Withholding Estimator or work through the worksheet printed on the form. If you or your spouse has self-employment income, the IRS directs you to the online estimator rather than the worksheet.
When you draw more than one pension or annuity, fill in Steps 3 through 4(b) only on the W-4P for the highest-paying one. Leave those steps blank on the forms for the smaller pensions. That keeps deductions and credits from being counted twice across payers.
Steps 3 and 4: Credits, Deductions, and Extra Withholding
Step 3 reduces withholding for tax credits you expect to claim, such as the credit for other dependents. Step 4 has three optional lines:
- Other income OPM doesn’t know about, which raises withholding.
- Deductions above the standard deduction, which lowers it.
- An extra flat dollar amount to withhold each month.
That last line is the simplest fix if you consistently owe at tax time and don’t want to run quarterly estimated payments.
Electing No Federal Withholding
You can check the “No withholding” box to have zero federal tax taken out. This makes sense only if your total income is low enough that you won’t owe federal tax. Guess wrong and you’ll owe the full amount plus a possible penalty in April. One restriction: if your payments are delivered outside the United States, you generally cannot elect zero withholding.
If You Submit Nothing
Not submitting a W-4P doesn’t turn withholding off. OPM applies the default, single with no adjustments, which over-withholds for many married or lower-income retirees. Filing even a bare-bones W-4P with the correct filing status can put money back into your monthly check.
How to Submit the Form to OPM
OPM accepts withholding changes through three channels.
Online Through Retirement Services Online
The fastest route is the portal at servicesonline.opm.gov. Sign in with your Login.gov credentials, then choose “Federal Tax Withholdings” or “State Tax Withholdings” from the menu. The portal walks you through the inputs directly, so there’s no PDF to complete or upload. The change is recorded immediately, and you can review it before you log out.
By Phone
Call OPM’s retirement line at 1-888-767-6738 with your claim number ready. This is a reasonable alternative if the portal isn’t comfortable for you but you don’t want to wait on mail processing.
By Mail
Sign the completed form and send it to:
Office of Personnel Management
Retirement Operations Center
P.O. Box 45
Boyers, PA 16017
Write your claim number on every page. Missing claim numbers are a leading reason mailed forms get delayed or misfiled. Mail is the slowest option and introduces manual data-entry risk, so check that every field is filled in and readable before you send it.
When the Change Shows Up on Your Payment
OPM processes annuity payments mid-month for delivery on the first business day of the next month. To catch the next payment, submit your change as early in the month as you can; requests made late in the month usually apply to the payment after that.
Once the change lands, verify your annuity statement in Retirement Services Online. If the withheld amounts don’t match what you requested, contact OPM right away instead of waiting until tax season to find the mistake.
Getting the Amount Right
The IRS charges an underpayment penalty if your withholding and estimated payments fall short of what you owe. The rate is the federal short-term rate plus three percentage points, compounded daily. In early 2026 that works out to roughly 7% annually on the shortfall, accruing each day you’re behind. You can avoid the penalty entirely by meeting any of these safe harbors:
- You owe less than $1,000 after withholding and refundable credits.
- Your total payments cover at least 90% of the tax on your 2026 return.
- Your total payments equal at least 100% of the tax shown on your 2025 return.
- If your 2025 adjusted gross income exceeded $150,000 ($75,000 if married filing separately), the prior-year threshold rises to 110%.
The prior-year rule is usually the easiest to hit. Divide last year’s total tax by 12 and make sure at least that much is withheld each month. If your income hasn’t shifted much, you’re covered.
Not All of Your Annuity Is Taxable
If you made after-tax contributions to your retirement plan, part of each monthly payment is a tax-free return of those contributions. The IRS calls the calculation the “Simplified Method” and lays it out in Publication 721, written for civil service retirees. Your W-4P elections apply only to the taxable portion, so setting withholding without accounting for the tax-free piece can leave you over-withheld. OPM reports both the gross distribution and the taxable amount on your annual 1099-R.
State Withholding Is a Separate Request
Form W-4P covers federal tax only. OPM can also withhold state income tax, but it doesn’t calculate the amount for you. You tell OPM a fixed whole-dollar amount to withhold each month, and that’s exactly what comes out. No allowances, no percentages, no brackets.
If you live in a state with no income tax, such as Alaska, Florida, Nevada, South Dakota, Tennessee, Texas, or Wyoming, you can skip state withholding entirely. Otherwise, estimate your state liability yourself or with a preparer, then submit the monthly dollar figure through the same portal, phone line, or mailing address you’d use for federal. Some states exempt pension income partially or fully, so check with your state tax agency before you set an amount.