ASMT-10 is issued under section 61 when the officer finds discrepancies in a GST return. It is not a demand. It is a question. The registered person replies in ASMT-11, within the time stated, with a reconciliation (GSTR-1 versus 3B versus e-way bills versus books) and, if tax is in fact payable, a payment. Silence can become a scrutiny or a show-cause. Do not treat it as spam. See GST.
Answer
How should a taxpayer respond to GST form ASMT-10?
It is a notice of discrepancies in returns. Reply in ASMT-11 with workings, within the time allowed.