The newest version of Form 943-X (to allow for corrections to the new lines added to the 2020 Form 943) is expected in mid-March 2021. In the meantime, for 2020: If adjusting 2019 or earlier, you may use the existing Form 943-X. If adjusting 2020 and not making any increase or decrease to the employer or employee share of social security tax or to any of the new COVID-related lines that were added to the 2020 Form 943, the IRS strongly recommends not using the existing Form 943-X, but rather waiting for the new Form 943-X revision to be released. If adjusting 2020 and making any increase or decrease to the employer or employee share of social security tax or to any of the new COVID-related lines, don't use the existing Form 943-X; instead, wait for the new Form 943-X revision. Please don't send a Form 943 with "Amended" (or similar notation) written on the form. If you have already done either (3) or (4) above, wait for correspondence to find out if the IRS was able to process the tax return or had to reject it. Given the backlog of paper forms and correspondence due to COVID-19, the IRS is unable to estimate when correspondence will go out.