Assessment under section 63: registration-related notices may produce tax demand with interest and a payment direction. Assessment under section 63 applies where a person remains unregistered despite liability or where cancelled registration may attract tax liability. Form GST ASMT 15 records taxpayer and SCN details, submissions, and the conclusion to drop proceedings or create a demand. Where demand is created, the order presents a table of assessed amounts-tax, interest, penalty and others-and specifies Act and place of supply if IGST applies. Interest is calculated up to the order date; the taxpayer must pay outstanding dues by a specified date and compute further interest until payment, failing which recovery proceedings may be initiated.