Small business invoice checklist
By Adrian Simpson, 20+ years building and running small web and IT businesses, and just as many years chasing down invoices that bounced back for a missing detail. Published Aug 2, 2026, updated Aug 14, 2026.
Two minutes before you hit send is the cheapest time to catch a mistake. After it's in an accounts inbox, fixing anything means reissuing, and reissuing resets the clock on getting paid.
Before you send
Read down this list against the invoice on screen. Any "no" is worth thirty seconds now and a week later.
☐ The invoice number is new and follows the last one
☐ Client name is spelled the way their accounts team writes it
☐ It's addressed to the person who approves payment
☐ PO number or quote reference is on it, if there is one
☐ Invoice date and a real due date, not just a term
☐ Every line says what the work was
☐ Quantities and rates multiply out correctly
☐ Discount comes off before tax
☐ Tax rate and tax amount are shown separately
☐ The total matches what you quoted
☐ Bank details or payment link are on the invoice itself
☐ Your contact details are on it
☐ Tax or company registration number, where that applies
The one that costs most. A total that doesn't match the quote. Even a $20 difference sends the invoice back for approval, and nobody tells you it happened. Check the quote before you send, every time.
Extra checks for a first invoice to a new client
The first invoice to anyone is the one most likely to stall, because you're guessing at how their process works. Five minutes of checking beats a month of silence.
☐ You have the legal entity name, not the trading name on their website
☐ You know whether they need a PO raised before you invoice
☐ You've asked what their standard payment run looks like
☐ The agreed price and terms exist in writing somewhere
☐ A deposit was taken, if the job warranted one
☐ Bank details were sent by a channel they can verify
The legal entity one catches people out constantly. "Acme" on the website is often "Acme Trading Ltd" or "Acme Group Holdings Inc" in their finance system, and an invoice made out to the wrong entity gets returned rather than paid.
Purchase orders matter more than they sound. In a company that runs on them, an invoice without a PO number has nowhere to go. Nobody rejects it, it just sits there, and you find out six weeks later when you ask.
If you're registered for sales tax or VAT
A tax invoice has requirements a plain one doesn't, and the client may be unable to reclaim anything if you get them wrong. That makes it their problem, which quickly makes it yours.
☐ The client's registration number, where the rules call for it
☐ Net amount, tax rate, and tax amount shown as separate figures
☐ The right rate for what you sold, not just your usual one
☐ Zero-rated or exempt lines labelled as such rather than left blank
☐ Reverse charge wording, if the sale is cross-border and qualifies
☐ Currency named explicitly on international invoices
Rates vary by what you're selling and where both parties are, and they change. Check the current rules for your situation rather than copying last year's invoice. The sales tax calculator handles the arithmetic once you know which rate applies, and sales tax vs VAT covers why the two systems behave differently.
Sending it
Send it as a PDF attachment, not in the email body, and name the file so it survives being saved to a folder full of other people's invoices. Something like Invoice-2026-014-AcmeCo.pdf beats invoice.pdf every time.
Put the invoice number and amount in the subject line. If the client has an accounts email address, send it there and copy your day-to-day contact, because the person you talk to is rarely the person who pays.
The week after
Note the due date somewhere you'll see it. A calendar reminder for the day after is enough. Most invoices that go badly late do it because nobody noticed for a month.
If you haven't had an acknowledgement within a few days on a large invoice, a one-line email confirming it arrived is worth sending. It's not chasing. It's checking the thing got where it was going while there's still time to fix it.
Once a month
The per-invoice checks stop individual mistakes. This one catches the money that goes missing quietly, and it takes about fifteen minutes.
☐ Chase anything past due, oldest first
☐ Check nothing was delivered but never invoiced at all
☐ Confirm the payments you received match the invoices you raised
☐ Check your numbering has no gaps you can't explain
☐ Flag any client who is late for the third time running
Work delivered and never invoiced sounds impossible until it happens to you. It's usually a small job squeezed in around a big one, and it's gone for good once enough months pass that raising it would be awkward.
That last line is a pricing decision more than an admin one. A client who is reliably 40 days late on Net 14 isn't on Net 14, whatever the invoice says. Either shorten their terms, ask for a deposit, or price the delay in. The payment terms guide covers the options.
Keeping records
Keep a copy of every invoice you issue, paid or not, and keep the numbering unbroken. If you void one, keep the number and mark it void rather than reusing it. Most tax authorities expect to see a complete sequence, and a gap is the kind of thing that turns a quick check into a long one.
Start from a clean one
The invoice generator lays the fields out in this order so most of the list takes care of itself. If you're building the invoice from scratch, the full walkthrough covers what goes in each field.
This is general guidance rather than tax or legal advice. Requirements differ by country and change over time, so confirm anything that matters with a professional near you.