How to Send an Invoice

Last reviewed on April 24, 2026.

Once an invoice is written, the way you deliver it decides how quickly you get paid. Sending is more than just attaching a file — it's the subject line, the wording, the format, the recipient, and the cadence of what comes next. This guide walks through the mechanics for small-business owners, freelancers, and contractors who are still doing invoicing by hand rather than through dedicated software.

Decide on the delivery channel before you write anything

The easiest way to slow down payment is to send an invoice the way the client can't easily process. Before you hit send, confirm how your client wants to receive invoices. The four common channels are:

• Email to a named person — the default for most small businesses and individual buyers.
• Email to an accounts-payable inbox — typical for mid-size and larger companies. Addresses usually look like [email protected] or [email protected].
• A vendor or supplier portal — some larger clients require invoices to be uploaded to their own system. You will usually be given login details when the job is onboarded.
• Postal mail — rare but still required by some public-sector and older industrial buyers.

If you don't know the channel, ask during the first project email. A single question like "Who should I send the invoice to, and do you have a preferred format?" saves weeks of delay later.

Choose the right file format

For 90% of outside-the-company invoicing, PDF is the right answer. A PDF looks the same on every device, can't be accidentally edited by the recipient, and can be printed and archived cleanly. Word and Excel files are fine internally or when the client specifically asks for an editable file, but they shouldn't be your default because the formatting can shift when opened in a different version of the software.

Most of the templates on this site can be saved directly as PDF. In Word, use File → Save As and choose PDF. In Excel, use File → Export and choose "Create PDF/XPS Document." In Google Docs, use File → Download → PDF Document (.pdf). If you started from one of the free templates here, PDF export is built in.

Write a useful subject line

The subject line is what determines whether the invoice ends up in front of the person who can pay it. A useful subject line has three elements: the word "Invoice," an identifier the client can match to their records, and the amount.

Compare these two:

• ❌ "Payment"
• ✅ "Invoice 2026-0147 — ACME Corp — $2,400 due 23 May"

The second version is already indexed for the client's accounts-payable team. It contains the invoice number (which matches whatever is on the PDF), the client's own name so it reaches the right person when forwarded internally, the amount, and the due date. If you've designed an invoice numbering system that encodes a year and a client code, the subject line writes itself.

Write a short, specific email body

A good invoicing email is three to five sentences. It acknowledges the work the invoice covers, states the amount and due date in plain numbers, points to the attached file, and names how the client can pay. Anything longer dilutes the call to action.

Worked example

Here is a body that works for most service invoices sent to a business client:

Hi Priya,

Please find attached invoice 2026-0147 for the website-redesign work delivered in April. The total is $2,400, due by 23 May 2026 (Net 30).

Payment details are on the invoice — bank transfer is the easiest, but the account also accepts Stripe and PayPal if that's more convenient. Happy to split it into two instalments if you'd prefer; just let me know.

Thanks again for the project.

Best,
Sam

A few things that make this email work: the invoice number appears in bold so it's skimmable, the amount and date are unambiguous, the payment options are specific without being overwhelming, and the tone assumes the client intends to pay on time.

Copy the right people

For invoices to small clients, sending to your main contact is fine. For invoices to bigger companies, copy the accounts-payable address if the client has shared one. This avoids the classic problem where the project lead forgets to forward the invoice and the payment deadline quietly passes. If your point of contact has mentioned a finance team, it's reasonable to write: "I've also copied [email protected] so they have the file on record."

Send from the email address the client already recognises

Send invoices from the same address you've been using for project communication, not from a separate "billing" account you've never used before. New sender addresses sometimes end up in spam filters — the client's payment team ignores what they can't see.

Save a copy and log the send

Before you close the message, save the PDF in the same place you keep your other business records, typically a per-client or per-year folder. If you use a spreadsheet or small bookkeeping tool, log the send at the same time: invoice number, date sent, amount, due date, client, and status ("sent"). You'll need this log when you follow up.

Follow-up cadence

Most late invoices are late for ordinary reasons — the client meant to pay, the invoice got buried, the approver was on leave. A short, polite reminder sequence handles the vast majority:

1. Day of due date — a one-line reminder, only if the invoice is unpaid that morning. Example: "Hi Priya, quick heads-up that invoice 2026-0147 for $2,400 is due today. Let me know if you need anything from me."
2. Seven days after due date — a slightly more formal reminder. Re-attach the original PDF in case the first email is buried.
3. Fifteen days after due date — move to the escalation process described in the late-payments guide. That page covers late fees, payment plans, and the point at which you should pause further work.

Common mistakes

• Attaching a Word file by default. Editable formats invite arguments. Use PDF unless the client asked otherwise.
• Sending at the end of the week. Invoices sent on Friday afternoon often sit unread until Monday — send on Monday or Tuesday when possible.
• Burying the amount. If the client has to open the PDF just to know how much they owe, you've added friction.
• Using different invoice numbers than the filename. Keep the filename, the PDF, the subject line, and your records aligned — otherwise the client can't reference it cleanly.
• Not naming the payment method. If the client doesn't know how to pay, they won't guess.

Quick checklist before you hit send

• PDF attached, not Word or Excel (unless the client asked).
• Filename includes the invoice number and your business name.
• Subject line contains "Invoice," the number, the client's name, and the amount.
• Email body names the amount, due date, and at least one payment method.
• Accounts-payable address is copied when the client has one.
• You've saved a copy in your own records and logged the send.

Related guides

• How to Write an Invoice: Complete Guide
• Invoice Payment Terms: Net 15, Net 30, and Beyond
• Handling Late Payments and Overdue Invoices
• Invoice Numbering Systems Explained