From FY 2023-24 on words those who opted Old Regime after due date [ 31st July ] automatically converted into New Regime.
Those who opted New Regime after due date late fee of Rs.5,000, which shall be reduced to Rs.1,000 if your total income is below Rs.5 lakh.

Section 80TTB of Income Tax Act

Under Section 80TTB to allows deduction on the interest earned on your savings account or fixed deposits with a bank, cooperative society, or post office.

A deduction of Rs 50,000 or the Income amount, whichever is lower.

Here Income amount means, aggregate: Interest on bank deposits (savings or fixed), Interest on deposits held in a co-operative society, Interest on post office deposits.

This Section is only for resident senior citizens (above 60 age).

This Section is applicable w.e.f. 1st April 2018.

It is applicable only an Old Regime.