How to Revise a Sales Tax Return After Digital Invoicing (2026): 120 Days, 60 Days and the Right Order

You filed your monthly sales tax return. Then you found a mistake — an invoice that was missing, a wrong amount, or input tax (the sales tax you paid on your purchases) you forgot to claim.

The law lets you correct a filed return. It is called a revised return, and section 26(3) of the Sales Tax Act 1990 gives you 120 days from the day you filed the original one.

This guide explains the 120-day rule, the 60-day shortcut that skips the Commissioner's approval, and the one thing digital invoicing changed: you now have to fix things in the right order, or the correction will not hold.

Section 26(3) of the Sales Tax Act 1990 says a registered person may file a revised return within 120 days of filing the original return, to correct any omission or wrong declaration in it.

The normal route needs the approval of the Commissioner Inland Revenue (the senior FBR officer who has jurisdiction over your case) before the revised return can be filed. You apply through IRIS, state what you are correcting and why, and wait for the approval to be granted.

Two limits are worth knowing before you plan anything. First, the 120 days run from the filing date of the original return, not from the end of the tax period and not from the day you noticed the mistake. Second, a return that was never filed at all and is now more than six months past its due date can only be filed with the Commissioner's approval as well.

If the correction means you owe more tax, you pay the short amount with default surcharge — the interest-style charge for paying late. Its rate sits in section 34 and moves with KIBOR, so check the current figure rather than reusing an old one.

There is a carve-out, and most honest corrections fall inside it.

You do not need the Commissioner's prior approval if the revised return is filed within 60 days of the original return, and one of these two things is true: the tax payable in the revised return is more than what you already paid, or the refund you are claiming is less than what you originally claimed.

Read that carefully, because it is a one-way door. The shortcut exists for corrections that go in FBR's favour — you are paying more, or asking for less. A correction that reduces your tax or increases your refund goes back to the normal approval route.

There is a second protection worth naming. If you find the mistake yourself and file the revised return voluntarily with the short-paid tax and default surcharge, before you have received a notice of audit, the penalty is not recovered from you. Catching your own error early is therefore cheaper than being told about it.

This is the part digital invoicing changed, and it is the mistake we see most often. A return used to be your own declaration, so a wrong number was just a number to correct. Now the return is fed by invoices that already sit on FBR's servers, each with an IRN (Invoice Reference Number — the unique number FBR gives every accepted invoice) attached.

So a revised return does not repair a wrong invoice. If the invoice itself carries the wrong value, the wrong buyer NTN or the wrong tax rate, you have to correct the invoice at FBR first, and then revise the return so the two agree.

The invoice side has its own clock. Under STGO 01 of 2026 you can edit or cancel a posted invoice within 72 hours of issuing it. After 72 hours the edit needs the Commissioner's approval too. That is a different 72 hours from the refund rule and a different approval from the return one — see FBR STGO 01 of 2026: Invoice Amendment, Cancellation & the 72-Hour Rule for the invoice side in full.

The working order is therefore: correct the invoice at FBR, confirm the new IRN record, then revise the return. Doing it the other way round leaves your return saying one thing and FBR's invoice record saying another, which is exactly the mismatch an audit looks for.

Three things, and each changes what a revision is actually for. Your sales side is now filled in for you. Posted invoices flow into Annexure-C, so the sales figures in your return are already FBR's figures. There is far less to revise on that side — and far less room to argue if it is wrong. How Digital Invoicing Feeds Your Sales Tax Return (Annexure-C) in 2026 explains the flow.

Your purchase side depends on other people. Input tax reaches your return through Annexure-A, and Annexure-A is filled from invoices your suppliers post. If a supplier posts late, your input tax appears in a later month than the purchase. Annexure-A After Digital Invoicing (2026): Your Purchase Register, Input Tax and the Missing-Invoice Problem covers what to do about it.

And a missing purchase invoice often does not need a revision at all. The Act lets you claim input tax you did not deduct in the relevant period in any of the six succeeding tax periods. An invoice dated March can still be claimed in the September return. Waiting for the next month is usually simpler, and cheaper, than applying to revise an old one.

A sale was left out of the return, and the invoice was posted late. The invoice already carries a valid IRN, so the invoice is fine. Revise the return to include it and pay the tax with default surcharge. If you are inside 60 days and paying more, no approval is needed. What Happens If an FBR Digital Invoice Is Generated Late? Backdating, Penalty and the Fix (2026) covers the invoice side of this.

A posted invoice has the wrong amount. Do not touch the return yet. Correct or cancel the invoice at FBR first, within 72 hours if you can, then revise the return to match the corrected record.

You forgot to claim input tax on a purchase. Check whether the invoice is sitting in a later Annexure-A. In most cases you claim it in a coming month under the six-period window instead of revising an old return.

You claimed input tax against an invoice your supplier never posted. This one needs action on both sides: ask the supplier to post it, and if the claim is already in a filed return, expect it to be disallowed until the invoice exists on FBR's record. Revising the return alone will not create the invoice.

In every case keep the paperwork together — the approval, the revised return acknowledgement and the payment receipt. If you paid a short amount, How to Pay an FBR Penalty: PSID, CPR and What to Do After a Digital Invoicing Notice (2026) shows how to make the payment count.

If you are still posting invoices by hand and finding these errors a month later, a connected system catches most of them at the moment of issue. You can create a free account on Digi Invoice and post directly to FBR from the invoice screen.

Revised return — a corrected version of a sales tax return you have already filed.

Section 26(3) — the part of the Sales Tax Act 1990 that allows a revised return within 120 days.

Commissioner Inland Revenue — the senior FBR officer whose approval a revision normally needs.

Input tax — the sales tax you paid on your purchases, which you set off against the tax you collected.

Default surcharge — the interest-style charge for paying tax late, set under section 34.

IRN — Invoice Reference Number, the unique number FBR gives an invoice once it is accepted.

Tax period — one month of sales tax, the period a single return covers.