I was having the same problem as everyone else with line 18. I didn't want my taxes deferred either and after some reading and experimenting I found the solution that worked for me.
Something is screwed up with line 18 and with that covid relief section. If you manually enter a number on line 18 you won't be able to adjust the deferral amount under the covid section where the fix is.
To not have your taxes deferred you have to answer YES to the question "Do you want more time to pay self-employment taxes" under that covid section in deductions and credits. This doesn't make any sense because it's the opposite of what you want to do. You can then put a dollar amount in that section that was earned between that time period and then go to the next question where it ask you for the amount you want deferred. I choose $0. After I did that I was able to complete the smart check with no problems.
