Sales tax invoice, explained field by field

The required fields

A valid sales tax invoice needs, at minimum: the seller's NTN and STRN, the buyer's registration details (if registered), an invoice number and date, a description of each item sold, the HS code and quantity per item, the value excluding sales tax, the sales tax rate and amount per item, and the final total including tax. Missing any of these is usually enough to cause a validation failure on submission.

Why the HS code drives everything else

The HS code assigned to each item determines its sales tax rate, and in some cases whether further tax, withholding tax, or an SRO-specific exemption applies. Get the HS code right, and the rest of the tax calculation follows automatically; get it wrong, and every downstream number on the invoice is wrong too, even if the arithmetic itself is done correctly.

A worked example, with numbers

Registered vs. unregistered buyers

A sale to a registered business buyer needs that buyer's NTN and registration type captured accurately on the invoice — this is what allows the buyer to claim input tax where applicable. A sale to an unregistered or walk-in customer doesn't need those details, but still needs the same accurate tax calculation on the seller's side.

Where these invoices usually go wrong in practice

In manually prepared sales tax invoices, the most common failure points are an HS code assigned from memory rather than looked up, a buyer NTN transposed or outdated, and a tax rate applied uniformly across a mixed order when different line items actually carry different rates.