How to write an invoice

An invoice has one job: get you paid without a follow-up email. This guide covers the required pieces, the terms that actually move money, and the mistakes that quietly add weeks to your cash flow.

The nine required pieces

Your business name and contact details — the legal name your clients' accounting software will match against.
The client's billing details — company name, address, and the AP contact if you know it.
A unique invoice number — sequential (INV-2026-001, -002…) so nothing is missing when someone audits.
The issue date — payment terms count from this date.
The due date — a real date, not just “Net 30”. Dates get paid; jargon gets filed.
Itemized work — description, quantity, rate. Specific line items answer objections before they form.
Tax — only if it applies to you; show the rate, not just the amount.
The total due — unambiguous, at the bottom, bigger than the rest.
How to pay — account details, payment link, or “card on file” instructions.

Payment terms that actually work

Net 14 is the sweet spot for most small businesses: long enough to feel professional, short enough that the work is still fresh in the client's mind. Net 30 is normal for large companies with formal AP cycles. “Due on receipt” sounds demanding and, paradoxically, gets paid slower than a specific date because there's nothing to schedule.

The three mistakes that delay payment

Vague descriptions. “Design services — October” invites questions; “Landing page design, 2 revision rounds included” doesn't.
No payment instructions. Every extra step between “I got the invoice” and “money sent” costs days.
Inconsistent numbering. If your numbers repeat or skip, a client's AP team can't match them to purchase orders — and unmatched invoices go to the back of the queue.

When to chase

Day 1 overdue: a two-line polite reminder with the invoice attached (most late payments are process, not malice). Day 14: firmer tone, state the late-fee policy if you have one. Day 30+: stop work per your agreement and move to a formal demand. Consistency beats intensity — the same boring reminder every time builds a reputation that gets you paid on time.

Ready to send one? The free invoice generator produces a clean, printable PDF in the browser — no account needed. For specific trades, start from a template.