Yes, it is too late if you have already filed you can not add the property tax to your return without amending your return.
However, if you took the standard deduction and did not itemize your deductions then the unreported tax payments may have no effect on your return.
The 2019 standard deductions are $12,200 if you are single or use married filing separate status $24,400 if you are married filing a joint return and $18,350 if you file as head of household.
[Edited 03/10/2020 | 9:55 am PDT]
