This form is to summarize your sales and use tax refund requests. The Total of all Refund Request Spreadsheets must equal the amount of refund requested.Note: You must complete a separate Form 3911 for each refund for which you are requesting information. Our goal is to stop fraudulent returns before they go out the door, not to slow down your refund. Check the box below that indicates your reason for filing Form 843. Tax. Abatement or refund of tax other than income, estate, or gift tax. The primary letter we use to request information about a return is Form DTF948 or DTF948O, Request for Information (RFI). All filers must complete this part. Page provides taxpayers and tax professionals the mailing address for submitting Form 843. Address your request and sample cover letter to your servicing IRS location.