I filed our 2019 Taxes in February of 2019. In April of 2020 I received a I received a Schedule K-1 I did not know we were getting. I filed an amended return in July of 2020 and enclosed a check for the amount due. The check was cashed in October of 2020. Today, March 15th, 2021 we received a refund of the amount we sent along with interest earned. I'm guessing the paperwork hasn't been processed. I'm inclined to cash the check, take copies and document everything and wait for the IRS to bill me. I don't want to pay interest to the IRS. If I have done my due diligence, copied all pertinent documents can the IRS charge us interest? What should I do.
