I just received a 1099-B, which the issuer filed an extension to issue. Unfortunately, I had already filed my taxes. After calculating the amended filing, the additional refunds owed to me are Fed $145 and State $39 because I had a net capital loss.
My question is since the 1099-B only shows sales and proceeds and not all equivalent cost basis, which is about $20k difference when input actual cost basis, do I still need to file an amendment for such a small amount of refund?