Does the extension to September 16, 2025 apply to filing Form 10IEA as well?

Yes, the extension covers it. Whenever ITR due date is shifted, related forms like 10IEA also get the same benefit. So you can file both till September 16, 2025 without any penalty.

Yes, because Form 10IEA has to be filed before or along with the ITR if you want to choose the new tax regime. Since the due date of ITR is extended, the deadline for filing 10IEA also shifts to September 16. Both are linked together.

As per rules, Form 10IEA must be filed on or before the ITR filing date. So, with the extension, the new deadline is September 16, 2025. If you miss that, you cannot opt for new tax regime for that year.