GST is a matching system. Your returns are continuously compared, against your suppliers' filings, your customers' claims and your own books. Businesses that reconcile monthly keep the differences small and correctable. Businesses that reconcile once a year discover them as notices, interest and lost credit.
The monthly reconciliations
These four checks, done at filing time each month, prevent most GST problems we see:
- Sales register to outward returns: every invoice in the books appears in the return, with the same value and tax. Credit notes and amendments included.
- Input tax credit claimed against credit available in the GST system: claim what is reflected and eligible; track what is missing and chase the supplier in the same month.
- Books to returns: GST payable and credit balances in the ledgers should match the return workings exactly. Differences mean an entry error on one side.
- Cash and credit ledger balances on the portal against the books, so payments and set-offs are recorded correctly.
The supplier problem
Most input credit losses trace to suppliers, invoices not uploaded, uploaded late, or uploaded with wrong details. Practical defences:
- Track credit that is in your purchase register but not reflected in GST records, supplier by supplier, every month
- Follow up within the month; a supplier who has not filed for one period will usually fix it when asked early
- For chronic defaulters, consider payment terms that hold back the tax amount until the credit reflects
- Before onboarding a significant new supplier, check their filing history, it is visible on the portal
The annual reconciliation
At year-end, the cumulative version of the same checks feeds the annual return, plus:
- Full-year turnover in GST returns reconciled to turnover in the audited accounts, with every difference categorised: timing, valuation, classification or error
- Input credit availed for the year against the annual credit statement, including the cut-off for claiming prior-year credit, credit not claimed within the prescribed window is lost
- Reversals reviewed: exempt supplies, personal use, blocked credits and non-payment to suppliers within the stipulated period
- Rate and classification review of major products and services, especially after any rate change during the year
When a notice arrives
Mismatch notices are increasingly system-generated, which means they are also answerable with system data.
- Do not pay reflexively, and do not ignore the deadline, both are expensive
- Trace the exact mismatch: which period, which supplier or invoice, which return
- Reply with a documented reconciliation showing where the difference comes from and whether tax is actually due
- Where tax is genuinely payable, paying early limits interest; where it is not, a clear paper trail usually closes the matter
Making it routine
The whole monthly cycle takes a few hours for a typical SME once the format is set up. The businesses that struggle are not the ones with complex operations (they are the ones that treat GST as a filing task instead of a reconciliation task. Set the monthly checklist, assign an owner, and review the exception list) missing credits, unmatched invoices, pending replies, at the same time as the filing each month.
If accumulated mismatches have already built up, deal with them in order of exposure: quantify, correct what can be corrected in current returns, and document the rest before the department asks.