How to Invoice a Client: A Step-by-Step Guide
Knowing how to invoice a client comes down to a repeatable sequence: put your details and theirs on a numbered document, list the work as itemized lines with hours and rates, total it, set a clear due date, and send it to whoever actually pays. Do that consistently and you get paid faster and chase less. This guide walks through writing your first invoice, what to include, and the small choices that decide whether the money arrives on time.
Getting it right matters more than it looks. The 2025 Intuit QuickBooks US Small Business Late Payments Report, a January 2025 survey of 2,487 US small businesses, found 56% were owed money on unpaid invoices, averaging about $17,500 per affected business, and 47% said some of their invoices were more than 30 days overdue. A clear, complete invoice sent to the right person is your first defense against ending up in that group.
What to include on an invoice
A complete invoice is a short, specific document. There is no universal US federal invoice template — invoices are governed by general contract principles and tax rules — but a payable one always carries the same fields:
| Element | What it is |
|---|---|
| Your details | Business name, address, email, tax/VAT number if you have one |
| Bill to | The client's legal entity, billing address, and AP email |
| Invoice number | A unique, never-reused identifier |
| Dates | The invoice date and an explicit calendar due date |
| Line items | One per task: description, hours or quantity, rate, line total |
| Totals | Subtotal, sales tax as a separate line where it applies, total due |
| Payment | Accepted methods and your payment terms |
Where sales tax applies, show it as its own line rather than folding it into the totals — it keeps the math legible for the client's accounts team and for you at tax time.
How to write an invoice, step by step
Once you have the fields, writing the invoice is mechanical:
- Number it. Assign a unique invoice number (more on the scheme below).
- Fill in both parties. Your details, and the client's correct "bill to" entity.
- Itemize the work. One line per task, with hours, rate, and line total.
- Total it. Subtotal, any sales tax, and the amount due.
- Set terms and a due date. A specific calendar date, not just a label.
- Send it promptly to the right person, with a short note stating the due date.
The first four steps are arithmetic over work you've already done. The last two are where most of the get-paid-on-time leverage actually lives.
Number every invoice in sequence
Assign every invoice a unique, never-reused number. There is no single US federal law that forces invoice numbers to be sequential, but a sequential scheme is standard practice and the default in accounting software, because it lets you spot a missing invoice, reconcile payments, and show a complete income record if your books are ever reviewed.
A few conventions are worth adopting from invoice one:
- Start at 0001, not 1. It looks established and leaves room to grow.
- Optionally prefix with the year, like
2026-001, and reset annually — or add a short client code. - Never skip or reuse a number. If you make a mistake, mark the invoice void and reissue with a new number rather than deleting it, so you don't leave a gap in the sequence.
If you bill clients abroad, this stops being optional. The EU VAT Directive and HMRC in the UK require a sequential number that uniquely identifies each invoice, and Australia's ATO requires a unique identifier (without mandating a strict sequence), so gaps or duplicates can become audit red flags. Confirm the exact rules for your jurisdiction.
Send it to the person who actually pays
The person who hired you is often not the person who pays you. At anything larger than a sole proprietor, invoices are processed by accounts payable or a dedicated billing contact, and sending yours only to your day-to-day contact is a common reason an invoice sits unrouted and "lost."
Before your first invoice, ask two questions: who or what email or portal should the invoice go to, and is a purchase order (PO) number required? Capture the correct legal business name and billing address while you're at it. The "bill to" entity that actually pays can differ from the contact you worked with, and getting it right up front prevents the invoice from stalling before anyone has even reviewed it.
How to invoice a client for the first time
A first invoice to a new client carries a little more risk than a repeat one, so the terms deserve thought. Net 7, Net 14, and Net 30 mean payment is due 7, 14, or 30 days after the invoice date; "due on receipt" means immediately.
| Term | Due | Best suited to |
|---|---|---|
| Due on receipt | Immediately | Small one-off jobs, deposits |
| Net 7 | 7 days | Fast cash flow, smaller invoices |
| Net 14 | 14 days | A balanced default for new clients |
| Net 30 | 30 days | Established clients, larger companies |
Net 30 is the most common B2B term, but shorter terms collect faster and are widely recommended for freelancers and new clients; Net 14 is the common balanced pick. Whatever you choose, put an explicit calendar due date on the invoice, not just "Net 14" — a date removes the ambiguity about when "soon" is. Invoice payment terms explained decodes Net 15, 2/10 Net 30, and the rest.
Two more levers help with a first client. By Xero's own account, invoices that include an online payment option — a "pay now" button — get paid up to twice as fast as those without one (a vendor figure worth confirming on Xero's site). And asking for an upfront deposit, commonly 25% to 50% due at contract signing before work starts, is a standard way to reduce the risk of non-payment and confirm the client's commitment. Strong reluctance to pay any deposit is itself a useful signal.
Itemize from tracked hours, not memory
The line items are where invoices get disputed or trusted. A defensible invoice has one line item per task or deliverable, each showing a specific description, the hours or quantity, the rate, and the line total — with the grand total being the sum of those lines, not a round number you reached for.
Itemized invoices are less likely to be disputed than a single vague line like "professional services," because the client can see exactly what they are paying for and why it took as long as it did. "Built homepage CSS — 3.5 hrs — $X" answers the question before it's asked.
The catch is that itemizing only works if the hours are accurate. Logging your time as the work happens — rather than reconstructing the month at billing time — keeps the numbers provable instead of estimated after the fact. That tracked time is the real source document behind the invoice; our guide on how to track billable hours covers capturing them without a timer to babysit, and PDF invoice generator for freelancers shows how a clean log turns into the finished document.
After you send, follow up on a schedule
Send the invoice promptly after the work is done, while it's fresh, with a short professional email that states the due date. Then keep a follow-up cadence ready: a polite reminder around the first day past due, escalating from there. Most late invoices aren't refusals — they're invoices that slipped down someone's inbox, which is exactly why a unique number, a clear due date, and an easy way to pay all earn their place.
Let your tracked time write the invoice
If you bill by the hour, the slowest part of invoicing isn't formatting the document — it's reconstructing where the hours went. That's the part worth automating.
BillNotch is a desktop time tracker for Windows, macOS, and Linux that records the active window automatically, with no timer to start. Keyword rules and optional AI sort your activity into client projects, billable is inherited per project, and the live billable total becomes a PDF invoice or a CSV export when you're ready to bill — itemized, dated, and scoped to the client you choose. The Revenue Leak Finder flags billable time you tracked but never invoiced, so hours don't fall through the gap between doing the work and charging for it. Window titles can stay on your device, you connect each device with an API key you issue and revoke, and data is processed on EU servers and never sold. Pricing is flat — Pro is $9/mo for one seat, Team is $12/seat/mo — with a 14-day free trial and no card required.
None of that replaces the judgment in this guide: who to bill, which terms, what deposit. It just means the line items and the total are a faithful record of the work rather than a month-end guess. Plans are on the pricing page, there's a worked walkthrough in how to invoice from time tracking, and if you bill by the hour, BillNotch for freelancers covers the workflow end to end.