Can I claim $2,084.41 in med. expenses pd. in 2021 on pymt. plan for 2020 incident? Already claimed $4,182 pd. in 2020.

You can enter the amount you paid in 2021 on your 2021 tax return.   What matters is when you paid the medical bill, not when the expense occurred.

MEDICAL EXPENSES

The medical expense deduction has to meet a rather large threshold before it can affect your return. The amount of medical (including dental, vision, etc.)  expenses that will count toward itemization is the amount that is OVER 7.5% of your adjusted gross income. You should only enter the amount that you paid in 2021—do not include any amounts that were covered by insurance or that are still outstanding.  Of course, your medical expenses plus your other itemized deductions still have to exceed your standard deduction before you will see a difference in your tax due or refund.

To enter your medical expenses go to Federal>Deductions and Credits>Medical>Medical Expenses

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

Yes.  Medical expenses are deductible in the year paid if you can itemize deductions.  And if the medical expenses are high enough to be useful.

The medical expense deduction for itemized deductions is basically the same since 2018, after the Tax Cuts and Jobs Act (TCJA). TCJA brought the percentage of income back down to 7.5% from 10%.  You may deduct only the amount of your total medical expenses that exceed 7.5% of your adjusted gross income.  So you can see that you still need a substantial amount before they will be beneficial and added to other allowed deductions.