The form called SchSE-T is the Schedule SE for the primary taxpayer on the return who is self-employed and subject to self-employment tax on profits.
Line 18 of the Schedule SE is asking the amount of self-employment tax was earned from March 27, 2020- December 31, 2020. This will calculate the maximum amount of SE tax attributed to the qualifying period of 2020 that can be deferred.
The Max deferral line 18 is showing you the maximum se tax that can be deferred this year on your tax return.
Changes to Schedule SE (Form 1040) for 2020.
New Part III has been added to Schedule SE to allow self-employed persons to figure a maximum amount of self-employment tax payments which may be deferred.
All maximum deferral amounts will be carried to Schedule 3 (Form 1040), and the total amount that you may elect to defer may be further reduced.
For additional information refer to the following link:
This is asking if you want to put off any of the taxes due that you didn't pay in for that year. If you don't want to defer any and it's still giving an error, just take out any input here and leave it blank. This should take care of the issue.