Hello. Based on the info provided by you, I assume that you had filed the respective returns but forgot posting the acknowledgement. I don't think that should be the reason for the demand. You need to check your intimation u/s 143(1) to check the actual discrepancy if any. In case you dont have the intimation copy then you can re apply for it on the IT efiling website. After going through the same a further course of action can be advised. Trust this clarifies your query. Feel free to call / get back in case of further clarifications. Thanking You. Regards, Rohit R Sharma BCOM, ACA, LLB-GEN, CERT. FAFP.