How the invoice generator works
Last updated 10 November 2026
An invoice tells a customer what they owe, for what and by when. This generator builds one from your details, the items you sold and the payment terms, and shows exactly what will print.
How it works
- Each line is quantity times unit price, less any discount, rounded to the cent. The totals are the sum of the lines.
- With Prices exclude VAT, VAT is added on top at the standard rate from this site. With Prices include VAT, the VAT is worked out from inside the total.
- The due date is the invoice date plus the payment terms.
Worked example
With the starting figures:
- The two example lines come to R 8 750.00 before VAT.
- Discounts included: R 250.00.
- The invoice total is R 8 750.00.
How to read the invoice
The table shows one row for every item. Each row is the quantity times the unit price, less any discount on that row. The total at the bottom is the sum of the rows, with VAT added or separated out depending on the option you chose.
The Payment due date is the invoice date plus the payment terms. If you choose payment on receipt, the invoice says so instead of showing a date. Customers use this date to plan their payments, so it helps to check it before you send the invoice.
What an invoice usually contains
Most invoices carry the same basic information. This is a general list, not a legal one. What a valid tax invoice must contain is set by the VAT Act, so check the current SARS requirements.
- Your business name, address and contact details.
- The customer’s name and address.
- A unique invoice number, so each invoice can be told apart.
- The invoice date and the payment due date.
- A short description of each item, with the quantity and price.
- The totals, and the VAT if you charge it.
- Your banking details and a payment reference in the notes.
Prices that include or exclude VAT
The two VAT options give different totals from the same prices. When prices exclude VAT, the customer pays the prices you typed plus VAT on top. When prices include VAT, the total stays at what you typed and the VAT is the part inside it.
Pick the option that matches how you quoted the customer. If you told them a price and they expect to pay exactly that, the second option keeps the total the same. If the invoice and the quote treat VAT differently, the customer will see a total they did not expect.
Common mistakes
- Reusing an invoice number. Numbers that repeat make records hard to follow.
- Leaving out the payment terms, so the customer does not know when to pay.
- Mixing prices that include VAT with prices that exclude it on the same invoice.
- Forgetting to add your bank details and a reference in the notes, so the customer does not know where or how to pay.
- Forgetting to save a copy. This page keeps nothing once you close it.
What this does not cover
The generator does not send the invoice, keep a record of what you issued or track whether it was paid. It does not know your customer or check your VAT status. If a customer is late, the payment reminder generator can help you write a follow-up.
Things to watch
- Only charge VAT if you are registered. Charging VAT without being registered is not allowed.
- Add your bank details in the notes so customers know where to pay.
- Keep a copy of every invoice you issue. This tool does not keep one for you.
- Use the browser’s print dialog and choose Save as PDF to make a PDF.
The invoice generator is a drafting aid, not tax or legal advice. Read the full disclaimer. For the VAT sums, see the VAT calculator.