Sales tax audit: what gets tested and how to be ready
A sales tax audit is a tracing exercise with a narrow question at its centre: does each figure in your filed return correspond to a transaction supported by a valid document? Everything painful about an audit follows from records that cannot answer that.
The four things that get tested
- Sales annexure to sales register to invoices. Does every issued invoice appear, is the serial sequence unbroken, are cancellations documented, and does the rate applied match the supply described?
- Purchase annexure to supplier invoices. Does each claimed input have a valid tax invoice from a supplier who was registered and active at the time, with all mandatory particulars, claimed within the permitted period?
- Declared turnover to accounting revenue. Do twelve months of returns aggregate to the revenue in your accounts and in your income tax return, with any difference explained?
- Carry-forward continuity. Does the input tax credit balance flow correctly from period to period without unexplained movement?
Defending an input tax claim
Input tax disallowance is the most common adjustment, and each disallowance traces to one of a short list of causes:
| Cause | What would have prevented it |
|---|---|
| Invoice missing a mandatory particular | Checking supplier invoices on receipt, before payment — invoice requirements |
| Supplier not active at the time of supply | A dated verification of supplier status retained with the voucher |
| Claim made outside the permitted period | Posting purchases in the month they belong to rather than when they surface |
| Input relating to exempt supplies claimed in full | A documented apportionment applied consistently — zero-rated versus exempt |
| Blocked category claimed | Configuring the chart of accounts so blocked inputs are coded as cost from the outset |
| No underlying invoice at all | Never claiming from a payment record alone |
We settle the taxable value, apportion input tax and file monthly with the right federal or provincial authority.
Avail our sales tax servicesThe turnover reconciliation
This is the document to have ready before you are asked, because it is the first thing requested and the hardest to build retrospectively. It should show, for each month and for the year:
- Declared taxable turnover per the return.
- Exempt and zero-rated supplies, separately.
- Total revenue per the accounting ledger.
- Each reconciling difference, named — timing, non-taxable receipts, recoveries, inter-branch transfers.
Maintained monthly this takes minutes. Built in retrospect from records nobody remembers, it takes weeks and rarely reconciles cleanly. It also feeds the annual comparison against your income tax return, which is examined independently — the income tax audit checklist.
The file to have standing
Why you were selected, and what each reason implies
| Selection reason | What it means | What to prepare first |
|---|---|---|
| Input-output ratio outside the sector norm | Your input tax is high relative to output | Production or margin records explaining the ratio |
| Supplier declared less than you claimed | An Annex A mismatch flagged automatically | The invoices behind the unmatched amount |
| Refund claim filed | Refunds are examined as a matter of course | The full claim file, indexed |
| Accounts revenue exceeds declared supplies | The turnover reconciliation, run against you | The schedule reconciling the two |
| Random or sector-wide selection | Nothing specific is alleged | The standing file, as it is |
Only the last row is neutral. The other four tell you what the officer already believes before the first meeting, and each points at a different document. Establishing which one applies is the first question to ask — preparing the wrong file is worse than preparing none, because it signals you have not understood what is being examined.
Audit powers sit in section 25 of the Sales Tax Act 1990, which lets the officer call for the records prescribed by section 22 and examine them. That pairing is the whole of an audit's shape: what can be asked for is what section 22 already required you to keep, so a business whose records genuinely meet section 22 has, by definition, already assembled the audit file.
- Per period: the filed return, both annexures, the payment challan, the acknowledgement, and the reconciliation working.
- Sales: the register at invoice level, the invoices, credit and debit notes, and the cancellation log.
- Purchases: the register at invoice level, supplier tax invoices, import documents, and the dated supplier status verifications.
- Apportionment: the method, the working, and evidence it was applied consistently.
- Carry forward: a schedule showing the balance period by period.
- Systems: where POS or digital invoicing applies, the transmission records reconciled to the return — POS integration.
Why you were selected, and what that tells you
Selection is largely driven by risk parameters rather than at random, which means the notice usually tells you something about what is being tested. The recurring triggers:
- Input tax claimed against suppliers who did not declare the corresponding output. The mismatch is visible on both sides.
- An input-to-output ratio out of line with comparable businesses in your sector.
- A persistent carry-forward credit with no obvious commercial reason such as exports or a capital phase.
- Declared turnover inconsistent with the income tax return, or with visible activity in banking and third-party data.
- Gaps in the invoice sequence across periods.
- Nil or minimal returns from a business with evident operations.
If you can identify which of these applies to you, you can prepare the specific reconciliation before the first request rather than responding to a general one. That single step tends to determine whether the audit runs for weeks or months.
Conducting yourself during the audit
- Diarise the response date the day the notice arrives and work to two days before it.
- Produce what is requested, completely, for the periods raised — and nothing outside that scope.
- Structure the production issue by issue, with your position and the supporting documents named against each.
- Respond in writing through the proper channel, so there is a record. Avoid settling points in conversation.
- Keep a register of every document produced and when.
- Where a record is genuinely missing, say so and produce alternative evidence. Never reconstruct.
If your registers are not currently at invoice level, that is the first thing to fix — it is a prerequisite for everything above. Bookkeeping that survives a review covers the structure, and we can assess where your records sit.
Sources
This guide is written against the official and clearly labelled professional references below. Rates, thresholds and portal procedures change between reviews, so open the primary source before relying on a figure.
- Sales Tax Basics (FBR)
- Sales Tax Act 1990, amended through 30 June 2026 (FBR)
- File a Sales Tax Return (FBR)
Questions people also ask
What is the most common sales tax audit adjustment?
Disallowed input tax. Usually because the supplier invoice lacked a mandatory particular, the supplier was not active at the time of supply, or the claim fell outside the permitted period. These are documentation failures rather than legal disagreements, which is why they are so hard to argue after the fact and so easy to prevent at the point of purchase.
How far back can a sales tax audit go?
Audits are conducted for defined tax periods, and record retention requirements are set to support that. Because the retention period is measured in years rather than months, records need to remain retrievable and readable well after the periods they relate to, and any routine destruction should be suspended entirely while a proceeding is open.
Our supplier has since deregistered. Does that invalidate our old claims?
What matters is the supplier status at the time of the supply, not today. A claim against a supplier who was properly registered and active when the supply was made is not retrospectively invalidated by later deregistration. This is exactly why the verification should be evidenced at the time — a check performed today cannot establish a position from two years ago.
Do we have to produce the accounting file itself, or just reports?
Expect requests that go beyond printed summaries to the underlying records, because the point of the exercise is tracing rather than reading totals. A business that can only produce reports is in a weaker position than one that can demonstrate the trail from return to ledger to invoice. Keep the accounting data accessible and not solely in a former accountant possession.
Can we fix invoices during an audit?
Obtaining a corrected supplier invoice where one was genuinely defective is legitimate and worth doing. Creating or backdating a document is not, and it converts a documentation problem into something far more serious. Where a record genuinely does not exist, say so and produce the best alternative evidence rather than manufacturing the original.
Send the tax year and the transaction or filing involved, and we will tell you what is actually required.
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