How to send a professional invoice

An invoice is a legal document that asks for money, triggers accounting entries, and records the terms of a sale. A sloppy invoice takes longer to get paid, creates tax problems, and occasionally ends up disputed. This guide walks through every field that should be on a proper invoice, the formatting that gets paid fastest, and the payment-terms tactics that move DSO from 45 days to 18.

The 10 fields every invoice needs

(1) The word “Invoice.” Seems obvious. A document titled “Statement” or “Receipt” may get routed differently by the customer’s AP system. “Invoice” is the magic word.

(2) Invoice number. Sequential, unique. INV- 2026-0142 format works. Required for your own accounting and for any client using a PO-matched AP system.

(3) Issue date and due date. Both explicit. Not “Net 30” — an actual due date (“Due: June 15, 2026”). Clients process faster when they don’t have to calculate.

(4) Your business details. Legal business name, address, tax ID (EIN in US, VAT number in EU/UK), phone, email. If you operate under a DBA, include both.

(5) Client details. Legal entity (not just “John” — “Acme Corp Inc.”), billing address, AP contact name, AP email. Wrong billing address is a top-3 cause of invoice delays.

(6) Line items. Each item: description, quantity, unit price, extended amount. Specific descriptions (“Web design services — April 2026”) beat vague ones (“services rendered”) because AP teams need context to approve quickly.

(7) Subtotal, tax, total. Show each separately. Total should be in a larger font — the AP team scans for it.

(8) Payment terms. Net 15 / 30 / 60, early-pay discount if offered (“2/10 net 30” = 2% off if paid within 10 days, else full amount due in 30).

(9) Payment methods and instructions. ACH details, wire instructions, check mailing address, Stripe or PayPal link. Make it easy — an invoice with only “check payable to...” gets paid slower than one with ACH + credit-card options.

(10) PO number (if applicable). If the client issued a PO, it must match. No PO on the invoice = no payment from a big-company AP system.

Professional formatting rules

PDF, not Word or Google Doc. Lockable, non-editable, consistent rendering.

One page. If you need more, summarize line items and attach a detail sheet. Many AP systems cap at one page for auto-routing.

Your logo at the top, small. Professional appearance matters more than you’d think — a logo-less Word doc looks like an individual; a branded PDF looks like a real business that will follow up.

Clear font. Arial or a similar sans-serif at 10–11pt for body, 14pt+ for the invoice total. Decorative fonts signal amateur.

Payment terms — what to ask for, and what you’ll get

Net 15 — aggressive. Some small clients will pay this; most enterprise won’t, because their AP cycles are monthly.

Net 30 — industry standard. Default unless you know otherwise.

Net 60, Net 90 — imposed by large enterprises. You can sometimes negotiate down but rarely fully.

Deposit + milestone payments — for project work >$10k. Typical: 30% on contract signing, 30% at milestone, 40% on delivery. Reduces your risk of working uncompensated if the engagement sours.

Retainer — fixed monthly, paid at the start of each period. Best cash flow structure if you can get it.

Early-pay discount math (2/10 net 30)

Offering 2% off for payment within 10 days (instead of the full 30-day window) is equivalent to a ~36% annualized discount rate. Steep but it works: many AP teams are incentivized to capture early-pay discounts, and you get paid 20 days sooner.

Good tactic when: you need faster cash, you’re billing larger amounts, or your cost of capital (or your line of credit rate) is high.

Bad tactic when: most of your invoices are small, the 2% is meaningful to your margin, or your clients usually pay on time anyway.

Send-day tactics to get paid faster

Send Tuesday or Wednesday morning. Monday gets buried in weekend email; Friday afternoon sits over the weekend. Mid-week invoices get reviewed same day.

Email subject: “Invoice INV-2026-0142 — Due June 15, Acme Corp.” Include the invoice number and client name; AP teams track by exact subject.

Body: 2-3 sentences. “Attached is invoice INV-2026-0142 for the April engagement, $8,400 total, due June 15. Payment methods listed on the invoice. Happy to answer any questions.” Short, professional, payment-oriented.

Send a second reminder at day 28. Short, polite nudge. Non-defensive. “Hi — just a heads up, invoice 0142 is due on the 15th. Let me know if you need anything.” 60% of “forgotten” invoices are paid within a week of this reminder.

What to do when an invoice is overdue

Day 31 (1 day late): friendly ping asking whether everything is in order.

Day 37 (1 week late): more direct. Reference the due date explicitly and ask for an update.

Day 45 (2 weeks late): escalate to a manager or procurement contact. Include a copy of the invoice and all prior emails.

Day 60+: formal past-due notice with mention of late fees (if your contract allows them — typical is 1.5% per month on unpaid balance). Consider halting new work on other engagements for that client until paid.

Day 90+: collections or small claims. Usually a last-resort option after you’ve exhausted direct follow-up.

Late fees — should you include them?

Contract language allowing 1–2% per month late fee on overdue invoices is standard and enforceable. Advantages:

Most clients will move your invoice up in the queue rather than pay the fee.

If it comes to small claims, the fee is collectible and covers some of your time cost.

Disadvantages: small-business clients may push back or resent the clause. Judgment call based on the clients you typically work with.

Tax handling — jurisdictional basics

US: sales tax only on physical products (generally) or certain services (varies by state). Most B2B services aren’t sales-taxable.

EU / UK: VAT on most sales. Rate varies (UK 20%, Germany 19%, France 20%, etc). Reverse charge applies for B2B cross-border within EU.

Canada: GST/HST/PST depending on province and product type.

When in doubt, consult an accountant — collection and remittance rules are strict and getting it wrong creates tax liability for you, not the customer.

Run the numbers

Generate a print-ready invoice with the invoice generator — line items, tax, payment instructions, PDF export. Pair with the hourly rate calculator to make sure your bill rate matches the margin you want, and the VAT calculator if you’re billing EU/UK clients.