How to Send an Invoice

To send an invoice, save it as a PDF, email it to the client's accounts-payable contact with the invoice number, amount and due date in the subject line, add a payment link if you can, and follow up a few days before it's due.

That's the whole job. The details below decide whether you get paid this month or spend next month asking "did you get my invoice?"

How to send an invoice, step by step

Create the invoice, check it against the quote or PO, export it as a PDF named with the invoice number, and email it to the client's accounts-payable contact with a clear subject line and payment instructions. Then log the send and schedule a reminder. Here are the steps in order:

1. Create the invoice with a unique invoice number, issue date, due date, line items and total. The free invoice generator does this in a browser with no sign-up.
2. Check the details against the quote or PO (here's what every invoice must include). A wrong PO number or billing name is a common reason accounts payable sends an invoice back.
3. Save it as a PDF named with the invoice number, such as INV-2026-0042-Harbor-Coffee.pdf. Word and Excel files can be edited by accident and look different on every screen.
4. Find the right recipient. For companies that's usually an accounts-payable email (ap@ or invoices@), with your day-to-day contact in CC.
5. Write a short email with the invoice number, amount, due date and how to pay. The invoice email templates below cover the first send and every reminder after it.
6. Attach the PDF and add a payment link if you accept card or ACH online.
7. Log that it's sent and put the first reminder in your calendar.

Which way should you send an invoice?

Email with a PDF attached is the default for most US small businesses, because every client can open it and it leaves a dated record. Add a payment link when the client pays by card, use the client's supplier portal when they require one, and send paper only when asked. The other methods each solve a specific problem:

If a client gives you a portal login, use it. An emailed invoice to a company that requires portal submission may never be processed at all.

How do you send an invoice through email?

Put the invoice number, your business name, the amount and the due date in the subject line, keep the body to four or five lines, attach the PDF and include a payment link. AP teams search their inboxes by invoice number, so the subject line does most of the work.

Subject line formula: Invoice [number] from [your business] – [amount] due [date]

For example: Invoice INV-2026-0042 from Northwind Design – $1,897.43 due Oct 31

A few details that save follow-up emails:

• Name the file after the invoice number. "Invoice.pdf" is the least searchable file name in existence.
• Put the key numbers in the email body too, not only in the attachment. Some people read email on a phone and never open the PDF.
• Send one invoice per email. Bundling three invoices in one email is how one of them gets missed.
• Keep the invoice number in every reminder's subject line, as the templates below do, so AP can pull up the full history with one search.

Should you attach a PDF or send a payment link?

Do both. The PDF is the record your client's accountant files; the payment link is what actually gets clicked. A PDF alone means the client has to log into their bank and type your details, which is exactly the step that gets put off until "after this meeting".

When a payment link makes the biggest difference:

• Small clients and consumers, who usually pay by card.
• Overdue invoices, where removing friction matters more than the card fee.
• Recurring invoices, where the client can save their payment method.

Larger companies often pay only by ACH or check through their AP system and ignore links. For them, put your bank details on the invoice itself, and have a completed Form W-9 ready to send through the client's vendor portal or secure upload when they ask for it, since many AP teams won't set up a new vendor without one.

Invoice email template you can copy

An invoice email should state the invoice number, what it covers, the total, the due date and how to pay, in four or five lines, with the PDF attached. Copy the five invoice email templates below, swap the brackets, and you have every email from the first send to a final notice.

1. Sending the invoice

2. Friendly reminder, three days before the due date

3. Due today

4. Overdue, seven days after the due date

5. Final notice, 30 days overdue

Only use template 5's late-fee line if your contract or quote actually includes a late fee, and keep the fee within your state's limits. Many states cap late fees and interest, especially on consumer accounts.

The line "if there's a problem with the invoice, I'm happy to fix it" matters. Sometimes a "late" payment is really an invoice stuck in approval over a missing PO number, and this line invites the client to tell you.

When should you send an invoice?

Send the invoice as soon as you've delivered the work, finished the milestone, or on the date your contract specifies. The due date is usually counted from the invoice date, so a week's delay in sending is a week's delay in getting paid.

If your client pays suppliers on a fixed schedule, ask which day invoices need to arrive to make the next payment run. One question can save you a full cycle of waiting.

How do you keep invoice emails out of spam?

Send invoices from an email address on your own domain, set up SPF, DKIM and DMARC records for that domain, and avoid link shorteners and image-only emails. Write a few lines of real text in the body instead of sending a bare attachment, and ask new clients to add your billing address to their contacts.

Since February 1, 2024, Google has required anyone sending to personal Gmail accounts to set up SPF or DKIM, and senders of 5,000 or more messages a day to set up SPF, DKIM and DMARC (Google's email sender guidelines).

A practical checklist:

• Use your domain: billing@yourbusiness.com, not a free webmail address.
• Authenticate the domain. Your email provider (Google Workspace, Microsoft 365) has a setup guide for SPF and DKIM; add a DMARC record after.
• Keep one sender. If invoices come from a tool, make sure it sends from your domain or a properly authenticated address.
• Use full links, not bit.ly-style shorteners.
• Put real text in the body. An email that's only an attachment looks like something spam filters are trained to catch.
• Ask new clients to add your address to their contacts or safe senders.

What should you do after you send an invoice?

Confirm a new client received it, then follow a reminder schedule you set on the day you send: a friendly note three days before the due date, a short note on the due date, and firmer follow-ups at 7, 14 and 30 days overdue. Here's a schedule that's polite but persistent:

When the payment arrives, mark the invoice paid and send a receipt or a thank-you. It closes the loop, and clients remember who made paying easy.

How do you send invoices automatically?

Connect the place your billing data lives (a spreadsheet, a CRM, a form) to an invoicing tool that creates, numbers and emails the invoice for you, then sends scheduled reminders and stops them once the invoice is paid. After setup, adding a row is all it takes to issue and send an invoice.

A typical no-code setup with Google Sheets:

1. Trigger: a new row in Google Sheets (customer, email, line items, due terms).
2. Action: a Webhooks by Zapier step (a premium app, so it needs a paid Zapier plan) sends the row to an invoicing API.
3. Result: the API issues the invoice, generates the PDF and emails it to the customer.
4. Write-back: the invoice number and the hosted invoice link go back into the row (a second Zapier step, Update Spreadsheet Row).

With the ASHDOCS Invoice API, one request can issue and email the invoice (set issue to true and add a send block): the email carries the PDF as an attachment plus a link to a hosted page your client can pay from when you connect Stripe. The email uses the subject and body from your settings unless you override them in the request. Before you switch any tool over, send a live invoice to your own email address (it uses one credit) and check its From and Reply-To lines against the spam checklist above.

You can schedule the send for later, and automatic reminders go out 3 days before, on, and 7 days after the due date, stopping as soon as the invoice is paid or voided. The 14- and 30-day steps in the schedule above stay with you. Each invoice records when it was sent, first viewed and paid, so "I never got it" becomes a solvable problem. The Zapier setup guide shows the Webhooks step, and the Google Sheets guide covers the spreadsheet side. On Make, the same flow uses the HTTP module (Make setup); on n8n, use the HTTP Request node (n8n setup).

How do you send an invoice on PayPal or Square?

Both let you create and send an invoice from their dashboard or app: you add the customer's email, line items and due date, and they email the customer a link to pay online. On both, you pay a fee when the customer pays through the invoice, not when you send it.

As of October 17, 2026, PayPal lists 2.99% + $0.49 for card payments on invoices, 3.49% + $0.49 when the customer pays with PayPal or Venmo, and 1% (capped at $10) for ACH (PayPal fees). Square's free plan lists 3.3% + 30¢ for card payments on invoices and 1% (minimum $1) for ACH (Square invoice pricing). Fees change, so check both pages before you choose.

They're a good fit if you send a handful of invoices a month and want payment built in. If your invoices start from a spreadsheet or another app, an API-based tool avoids copying the data across by hand.

Frequently asked questions

How do I send an invoice to a client? Export the invoice as a PDF, email it to the client's billing or accounts-payable contact with the invoice number, amount and due date in the subject line, and include how to pay. Add a payment link if you accept online payments, and set a reminder for a few days before the due date.

How do I send an invoice through email? Attach the invoice PDF, use a subject like "Invoice INV-0042 from [Business] – $500 due Oct 31", and write a short body with the amount, due date and payment options. Send one invoice per email and name the file after the invoice number.

What should I write in an email when sending an invoice? Greet the client, state the invoice number, what it covers, the total and the due date, then explain how to pay and offer to fix anything that's wrong. Four or five lines is enough; the details belong in the PDF.

When should I send an invoice? Send it the day the work is delivered or the milestone is complete, or on the date your contract sets. For ongoing work, invoice on a fixed day each week or month so clients can plan for it.

Is it better to send an invoice as a PDF or Word file? PDF. It looks the same on every device, can't be edited by accident, and is what most accounts-payable teams expect. Keep the Word or Excel version only as your editable source.

What is an electronic invoice? An electronic invoice, or e-invoice, is an invoice sent as structured data that the buyer's accounting system can read directly. An emailed PDF is digital but not structured. There's no federal B2B e-invoicing mandate in the US today; adoption is voluntary, for example through the exchange network overseen by the Digital Business Networks Alliance, so emailed PDFs remain standard for most small businesses.

How to send an invoice: the short version

Send the invoice as a PDF the day the work is done, to the person who actually pays, with the invoice number, amount and due date in the subject line and a payment link in the body. Send from your own authenticated domain, remind the client before the due date, and follow a fixed schedule after it. If your invoices start in a spreadsheet, automate the sending and reminders so none of them depend on you remembering.

Sending invoices from a spreadsheet every month? The ASHDOCS Invoice API issues, emails and reminds for you.