Self employed still need guidance from the IRS on exactly how to pay deferred social security using EFTPS. The EFTPS site has added an option for "deferred social security" but also requires that you enter a tax period consisting of year (2020) AND MONTH. At first I thought "December" would be appropriate since I am filing form 1040 as a calendar year tax payer. But entering December returns the error "Invalid Period." Leaving the month blank also returns an error. I'm not comfortable "guessing" what to enter here so at this time EFTPS is not an option.
