Business & Corporate · Section 8B
Sales Tax Return Calculator
Output tax less input tax, with the 90% input adjustment cap applied and any excess credit carried forward.
Enter tax amounts directly instead (optional)
Step by step
How the return math works
Work out output tax
Sales tax charged on your taxable supplies this period.
Work out input tax
Sales tax paid to your suppliers on taxable purchases.
Apply the 90% cap
Input adjustment is limited to 90% of output tax; the rest carries forward.
Settle the balance
Pay what remains, or carry excess credit into the next period.
Reading the result
The 90% cap is where returns surprise people
Input tax cannot wipe out output tax entirely. The adjustment is limited to a proportion of output tax, so a period where your inputs nearly matched your outputs still produces something to pay.
Businesses that plan cash on "input roughly equals output, so nothing due" find the shortfall at filing. The cap is the reason.
Excess input is carried forward, not lost
Input tax disallowed by the cap, or exceeding output tax, generally carries forward to later periods rather than disappearing. Over a run of months that builds a real balance. It is an asset worth tracking, and businesses that do not carry it forward accurately simply forfeit it.
Not every input is claimable
Input tax on goods and services that do not relate to taxable supplies, and on categories specifically excluded, cannot be claimed however genuine the invoice. Claiming broadly and adjusting later is how audit exposure accumulates — the safer habit is to classify at the point of entry.
Where this stops
This computes the position from totals you enter. The return itself also requires invoice-level detail, supplier verification and reconciliation against your suppliers' declarations — and a supplier who did not declare your invoice can put your input claim in question regardless of what your own records show.
FAQs
Sales tax return FAQs
What is output tax and input tax?
Output tax is the sales tax you charge your customers on taxable supplies. Input tax is the sales tax you paid your suppliers on taxable purchases. You pay the difference to FBR rather than the full output tax.
What is the 90% input tax cap?
Section 8B of the Sales Tax Act 1990 limits input tax adjustment for most registered persons to 90% of output tax in a tax period; input tax above the cap is carried forward, not lost. The Finance Act 2026 added a proviso letting the Board reduce or enhance that limit for a particular registered person according to their compliance with production monitoring, digital invoicing, e-bilty, POS or other electronic systems — so the cap is no longer uniformly 90% for everyone. Change the figure here if a different limit has been set for you.
What happens to excess input tax?
Input tax disallowed by the cap, and any input tax exceeding your output tax for the period, carries forward as a credit against future periods. It is not refunded automatically — a separate refund claim applies only in specific cases such as zero-rated exports.
Why can I enter either sales or tax amounts?
If you already know your output and input tax figures, enter them directly. If you only have taxable sales and purchase values, leave the tax fields blank and the calculator derives them at the rate you set. A directly entered tax amount always takes precedence over the derived figure.
Is this the same as filing my return?
No — this reproduces the core arithmetic of the monthly return so you can check a figure or plan cash flow. Actual filing requires reporting supply-wise detail in IRIS, and further adjustments (e.g. fixed assets, apportionment between taxable and exempt supplies, withheld sales tax) may apply to your case.
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