Located in West Virginia. Recently diagnosed with serious degenerative illness. I meet the 40 part of the 40/20 formula. But I have been self employed and took max deductions for a better return so now short on Credit Quarters by 4. I sell through Etsy and file through H&R B, so income and expenses can all be proven. Is it allowable by IRS to amend (2) tax year filings in which I had stated a loss and pay all incurred penalties and interest in order to meet 20 quarters requirement? Also is the 20 quarters needed over 10 years or 15, I found some conflicting information.