Can I add a sales tax for a car i bought in 2021 to my taxes 2024? I never added it before

No, you cannot put sales tax for a car purchased in 2021 on your 2024 tax return.   If you want to amend your 2021 tax return to include the sales tax you can do that.   Understand that sales tax is an itemized deduction that goes on Schedule A with mortgage interest, medical deductions and charity donations.   If your itemized deductions do not exceed your standard deduction, adding sales tax will have no effect on your refund or tax due.

Did you itemize for 2021?   What is on line 12 of your 2021 Form 1040?

2021 STANDARD DEDUCTION AMOUNTS

SINGLE $12,550  (65 or older + $1700)

MARRIED FILING SEPARATELY $12,550  (65 or older + $1350)

MARRIED FILING JOINTLY $25,100  (65 or older + $1350 per spouse)

HEAD OF HOUSEHOLD  $18,800  (65 or older +$1700)

Legally Blind + $1350