Deductions & credits

Uh oh!  I was afraid of that after reading up on all of the 179 details this year.  

I have not been reporting accurately for every year because I have used standard mileage for 2017-2019, and had planned to do so again for 2020..  Are you able to offer a suggestion on what I should do at this point?  2020 was my 5th and last year in my small direct sales business.  Do I need to amend the previous year returns? I'll appreciate any thoughts/advice/help...