IT Return: Can a tax payer choose between the old/ existing regime and new regime under the section u/s 115BAC?

Yes for salaried tax payer and No for non salaried tax payer.

For Salaried Tax Payer

A salaried taxpayer can choose the new tax regime at the beginning of FY 2020-21 and intimate their employer. The employee cannot change their choice anytime during the financial year. However, the change can be done at the time of filing the income tax return in July 2021.

The due date for tax filing for the FY 2020-21 (AY 2021-22) is 31st Dec 2021 (extended from 31st July 2021).

In case an employee does not choose the new tax regime at the beginning of the financial year, the employer will deduct tax (TDS) under the existing tax regime. Hence, a salaried taxpayer can opt-in and opt-out every year. That means you can choose the new tax regime in one year and choose the regular tax regime in another year.

For Non Salaried Tax Payer

A non-salaried taxpayer has to choose the new regime at the time of filing the tax return. They need not declare or intimate their choice to anyone at any time during the year. However, a non-salaried taxpayer cannot opt-in and opt-out of the new tax regime every year. Once a non-salaried opts out of the new tax regime, they cannot opt-in again for the new tax regime in the future.