My return has been marked defective under section 139(9) for a mismatch in gross receipts. How do I fix it within 15 days?

Fix: respond through e-Filing → Pending Actions → e-Proceedings → the 139(9) notice, choose "agree", and upload a corrected return in response to the notice within the 15 days (you can ask for an extension on the same screen if you need it). The corrected return is prepared offline in the utility: use ITR-4 if you want the freelance receipts taxed on the presumptive basis under section 44ADA (50% of receipts as income, no books), or ITR-3 if you want to claim actual expenses. Report the salary exactly as before, add the professional receipts under business or profession, and make sure the 194J TDS is claimed against that income.

Use the original return's acknowledgement number and date in the response; the corrected return relates back to the original filing date, so there is no late fee and the regime you chose stands.

If you do nothing, the return is treated as invalid after the period, which is the same as not having filed: late fee, loss of the old regime option if you chose it, and the TDS refund stays blocked.