Is relief under Section 89 1 available under new tax regime?

Hey Vinoth! Your understanding is correct:

Relief under Section 89(1) (which is for arrears or advance salary received and helps avoid tax on “bunching” of income) is NOT available under the New Tax Regime (Section 115BAC).

Why?
The New Tax Regime offers concessional tax rates but without most exemptions and deductions, including Section 89(1) relief.

So if you have opted for the new tax regime, you cannot claim relief under Section 89(1). It is only available for taxpayers sticking to the old (existing) tax regime with exemptions/deductions.

Your linked source from MargCompusoft is accurate in this regard.

Section 89(1) relief is available under the new tax regime. The restriction under the new regime applies to deductions under Chapter VIA like 80C and 80D, not to Section 89. Section 89 is a computational relief for spread-year taxation of arrears received in a lump sum, not a deduction. You do still need to file Form 10E on the portal before submitting your ITR, regardless of which regime you have opted for.