How long do I have to respond to IRS Letter 510C?

Return the check or respond by the date shown. Check the date and any response deadline printed on your notice, and follow the notice's instructions.

What should I do if I received IRS Letter 510C?

The IRS says a refund was issued in error and asks you to return it. Do not cash the check while you sort it out. If you are unsure, have a tax professional review the letter before you respond to the IRS.

IRS Letter 510C: Refund Issued in Error, Return the Check

Letter 510C says the IRS sent you a refund by mistake and wants it back. Do not cash it. If you already did, act before interest builds.

Numbers covered by this guide

Letter 510C
Ltr 510C
Letter 510-C
510-C
Refund in Error

Check the identifier and follow the instructions on your own notice.

Published by the Law Offices of Darrin T. Mish, P.A.Updated October 13, 2026

Notice: Letter 510C / Ltr 510C / Letter 510-C / 510-C / Refund in Error
Urgency: Urgent
Deadline: Return the check or respond by the date shown

Your first move

The IRS says a refund was issued in error and asks you to return it. Do not cash the check while you sort it out.

Letter 510C, Refund In Error; Return Check, tells you the IRS issued a refund it now believes you were not entitled to and asks you to send it back. Common causes include a payment applied to the wrong account, a duplicate refund, a refund issued before an adjustment posted, or a processing error on a return.

If You Have Not Cashed It

Don't. Follow the instructions in the letter to return the check. Holding or depositing it only creates a balance that will have to be unwound later.

If You Already Cashed It

Find out why the IRS says the refund was wrong before you pay it back. Pull your account transcript and compare it with your records. If the IRS is right, repay it promptly, because interest can accrue on an erroneous refund. If the IRS is wrong, respond in writing with documentation showing you were entitled to the money.

Large or Disputed Refunds

The IRS's tools for recovering an erroneous refund depend on why the refund was wrong, and some require it to act within strict time limits. If the amount is significant and you believe the refund was correct, get advice before you send anything.

If you received Letter 510C, call us at (813) 229-7100.

This letter has a clock on it. Don’t run it out alone.

Free consultation with Darrin T. Mish, a Tampa tax attorney licensed since 1993 and admitted to the U.S. Tax Court. Bring the letter.

Call (813) 229-7100

Request a consultation online