ITC is legal.

This discussion clarifies that Input Tax Credit (ITC) is generally claimable even if the supplier's GST registration is cancelled in a later financial year, provided the ITC was availed in compliance with Section 16 requirements during the relevant financial year (e.g., 2018-2019). Accumulated ITC can be set off in subsequent years, and the subsequent cancellation of the supplier's GSTIN should not impact your eligibility if all conditions were met initially.