Where do I mail my W-4V to?

You should mail your W-4V (Voluntary Withholding Request) form to the payer from whom you want to have federal income tax withheld, such as your pension plan or Social Security administration. Each payer may have a specific address for receiving tax forms, so it's best to check their website or contact them directly for the correct mailing address. If you're unsure, you can also send it to the IRS, but typically it goes directly to the payer.