Credit follows the supplier’s filing
You can claim input tax credit on a purchase only when the supplier has reported the invoice in their GSTR-1 and it appears in your GSTR-2B. A bill in your books that the supplier never filed is credit at risk, however genuine the purchase.
What a monthly match finds
Bills the supplier has not filed yet: ask them to file before you claim. Invoices the supplier filed that are not in your books: a bill you forgot to enter, or a purchase you did not make. Amounts or invoice numbers that differ: usually a typing mistake on one side.
Doing it in minutes
Download GSTR-2B from the portal as JSON, load it into OSuite, and each supplier invoice is matched to your posted bills by supplier, number and amounts. You work through the short list of exceptions instead of the whole month.
Why monthly
Suppliers fix their returns more readily for last month than for last year, and your GSTR-3B claim is then based on credit that is actually there.
General information, not tax advice; rules change, so check with your accountant for your case.