If you did not receive the tax bill for your supplemental taxes until after you filed your 2021 tax return, this means you did not pay them in 2021, therefore they would not be deductible on your 2021 return. You will need to wait until 2022 to claim them on your federal taxes.
If you paid supplemental taxes in 2021 and you want to enter them on your return, then you would need to Amend Your Return to include the taxes you paid in 2021 on your 2021 return.
If your mortgage interest, property taxes, medical expenses in excess of 7.5% of your AGI were lower than your standard deduction on your original return, unless the supplemental taxes bring your itemized expenses up to a point they are greater than your standard deduction, adding this to your return will not make any difference so then you would not need to amend your return.
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