ITR Defect Notice 139 (9) Received (Earlier ITR filed under old tax regime)

Hi Team,

I received defect notice 139(9) post submission of my ITR -1 with old regime.

The notice says it mis-matched the income from my 26AS , However I inlcuded all income mentioned  in 26AS in ITR-1 . but the defect is came as under 26AS along with my salary income there is one business income (section 194c) present which I consider as other source of income while filing the ITR-1.

Now, I realize I have to file ITR-4 for AY-2024 - 2025. 

issues :

1. To response the defect notice with failing the ITR-4 it not allowing me to file it under old tax regime
2. I have filed Form 10-IEA  (filled on 4th Aug 2024) Although it not allowing me to opt for old regime

Please help me here with you kind guidance.

As well as please let me know , if in case I did not response to the defect notice within allowable timeline what can happend ? (as I have mentioned all the income in ITR-1 as per 26AS just the business income mentioned as other source of income.

Thanks