Mailing Addresses for Form 843 IF you are filing Form 843... THEN mail the form to… In response to an IRS notice regarding a tax or fee related to certain taxes such as income, employment, gift, estate, excise, etc. The address shown in the notice. To request a claim for refund in a Form 706/709 only tax matter. Internal Revenue Service Center Attn: E&G, Stop 824G 7940 Kentucky Drive Florence, KY 41042-2915 For penalties, or for any other reason other than an IRS notice (see above), an estate tax claim for refund (see above), or Letter 4658 (see below) The service center where you would be required to a file a current year tax return for the tax to which your claim or request relates. See the instructions for the return you are filing. In response to Letter 4658 (notice of branded prescription drug fee) Note. To ensure proper processing, write “Branded Prescription Drug Fee” across the top of Form 843. Internal Revenue Service Mail Stop 4921 BPDF 1973 N. Rulon White Blvd. Ogden, UT 84404 Caution. Use this address only if you are claiming a refund of the branded prescription drug fee. For requests of a net interest rate of zero The service center where you filed your most recent return.