Invoices for sole traders, without the software

The sole trader invoicing setup that takes ten minutes

Working for yourself means the invoicing is on you, and the two failure modes are equally expensive: sending something that looks like it was typed in Notepad, or spending an hour a week on admin that should take four minutes.

Get these four things right once and the rest is repetition. Use your trading name consistently — whatever is on your bank account and, if you have one, your GST registration, because a mismatch between the name on the invoice and the name on the account is a genuine reason for a payment to be held. Number sequentially from one series, not per client. Put your bank details and a reference on every invoice, because the easiest invoice to pay gets paid first. And invoice the day you finish, not at month end.

On GST: below $60,000 turnover in New Zealand (or $75,000 in Australia) you do not have to register, and if you sell mostly to consumers you probably should not — adding 15% to your price to hand it straight to Inland Revenue makes you more expensive with nothing to show for it. If your clients are GST-registered businesses, they claim it back and it costs them nothing, so registering is usually the better call. Either way, set the tax mode here to match and the invoice wording follows automatically.

What a compliant tax invoice has to contain

An invoice is a request for payment. A tax invoice is also the document your client uses to claim back the GST they paid you — which is why tax authorities are specific about what has to appear on it, and why a missing field can hold up your money while an accounts department sends it back.

In New Zealand the rules were modernised in 2023 and the old requirement to hold a formal "tax invoice" was replaced by taxable supply information. The practical checklist did not really change:

• The words Tax invoice in a prominent place, or a clear indication that the document is one.
• Your registered business name and GST number.
• The date the invoice was issued.
• A description of the goods or services supplied, with quantities where relevant.
• The amount payable and the GST charged — either shown separately, or the GST-inclusive total with a statement that GST is included.
• For supplies over $1,000, the buyer's name and address as well.

If you are not GST registered

Do not charge GST, do not show a GST line, and do not call the document a tax invoice. Set the tax mode to No tax and the heading changes to "Invoice" automatically. Charging GST when you are not registered is a genuine problem, not a technicality — you would be collecting tax you have no right to collect.

Registration becomes compulsory in New Zealand once your turnover passes $60,000 in any twelve-month period, looking both backwards and forwards. Below that it is a choice, and it is not automatically the right one: registering means charging your customers 15% more and filing returns, which is worth it if your clients are businesses claiming it back, and often is not if they are consumers.

Invoice numbering, dates and getting paid faster

Your invoice numbers need to be unique and sequential. That is the whole rule. INV-0001 upwards is perfectly good; adding the year (2026-014) makes end-of-year filing easier; per-client prefixes (ACME-007) help if you invoice a handful of large accounts. What you must never do is reuse a number or leave gaps you cannot explain — both make a GST audit slower than it needs to be.

Payment terms are where most small businesses quietly lose money. Three things move the needle more than chasing:

1. Invoice the day the work finishes, not at the end of the month. Payment clocks start when the invoice arrives, so a week of delay on your side is a week added to your own wait.
2. Put the due date on the invoice as a date, not as "14 days". "Due 12 August 2026" is unambiguous; "payment terms: 14 days" invites a debate about when the clock started.
3. Make paying trivial. Bank account number, and a reference that matches the invoice number, on the invoice itself. Every extra step is another day.

If an invoice goes past due, a short factual email on day one beats a stern one on day thirty. Most late payment is administrative, not hostile — the invoice went to the wrong inbox, or it missed a payment run.