Can tax regime be changed in updated return

Updated return will be processed only under OLD tax regime...

Can we claim additional Tax deductions in the updated return ? Since the regime can't be changed to new, Can I show deductions under 80C/80D  in the updated return ?

Yes, provided there is additional tax liability...... or no reduction of taxability.

Thank you sir.

Here is the summary of the Issue 

I am salaried person and During my original file return for last assessment year(before the deadline i.e 31st July 2022), I selected the old taxation regime by mistake and paid taxes based on the new taxation regime, but a demand notice  was generated to settle the remaining tax liability.

Recognizing my mistake, I promptly submitted an revised return before the deadline (i.e., prior to December 31st, 2022), opting for the new regime to rectify the error. Despite filing the revised return under the new regime, the income tax department has issued an outstanding demand notice, calculating taxes based on the old regime.

One thing I understood after all this, that I cannot change the regime to new at this point in time.

However  based on your response If I understand correct, I can't reduce my tax by claiming deductions under 80C and 80D as per old regime at this point in time as there will be reduction of taxability. P.S: I have not declared Schedule 6A in my original return nor in revised returns.

Due to this simple mistake, I find myself in a situation where I have to pay tax around 38K. Is there any way to prevent this now? Won't I be having chance to claim these Schedule 6A deductions now? Will going appeal on this case helps?

NO. As the deductions under chapter VIA was not claimed in original return, now it is not possible. Filing appeal would have helped you if you had revised return under old regime only by claiming with Chapter VIA deductions.

Many taxpayers have suffered for the same mistake..

Good luck for next time.