You can switch to any regime while filling ITR, but condition is you can claim deductions like lic, medical, interest on home loan, rent etc only if you have receipts.

My salary slip mentions premium deduction for parents and self insurance, will that work for 80 D deduction?

Consultant

No that's not a proof, require mediclaim premium receipt.

Chartered accountant 

It was a mistake that I selected the new regime thinking that it would be easy to switch back to old one during ITR Filing, but now I do not have proofs such

It was a mistake that I selected the new regime thinking that it would be easy to switch back to old one during ITR Filing, but now I do not have proofs such as the premium amount paid (for parental and self insurance taken from company), sodexo vouchers received, since nothing is mentioned in the Form 16. Is my salary slip enough for showing as proof if I receive a notice, or is it necessary to have separate receipts for these deductions that I will be claiming? Anyone else in a similar condition as I am, please share your experience.

ITR Filing hassles