Send it to the person who pays, not the person you know

The most common reason an invoice is late is that it went to the wrong inbox. Your day-to-day contact approves work; accounts payable pays for it. Ask for the accounts email at the start of an engagement, and send there with your contact copied in.

Before you send

  • The customer’s legal name is right
  • The purchase order number is on it, if they use one
  • The invoice number has not been used before
  • The totals are correct and the due date is a real date
  • Payment details are on the document, not only in the email
  • It is a PDF, named so it can be found later

Writing the email

Short, specific, and structured so it can be found again by searching.

Subject: Invoice INV-014 — Riverbend Design — 1,310.00 due 24 April 2026

Hello Sam,

Please find attached invoice INV-014 for the homepage and product page redesign, per purchase order PO-88213.

Amount due: 1,310.00. Payment terms Net 14, due 24 April 2026. Bank details are on the invoice.

Any questions, reply to this email and I will come straight back to you.

Thanks,
Alex

Everything a payments clerk needs is in the subject line and the first two sentences: what it is, what it relates to, how much and by when.

Need the invoice now? The free invoice creator does the arithmetic and downloads a PDF. No signup.

Sending by other channels

  • WhatsApp or messaging. Normal for domestic and trade work. Send the PDF, not a photograph of a screen — the customer may need to forward it to an accountant.
  • Customer portal. Larger organisations often require submission through a supplier portal, and an emailed invoice is simply ignored. Ask during onboarding.
  • Printed. Still the fastest route for domestic work: handed over on the day, paid on the day.
  • E-invoicing networks. Some countries mandate structured electronic invoicing for certain transactions, particularly with government. Check whether it applies to you.

After you send

  1. Record it

    Number, date, customer, amount, due date, and where you sent it.

  2. Confirm receipt for large invoices

    A short note a couple of days later. “Lost in spam” is a real and frequent cause of a month’s delay.

  3. Reminder just after the due date

    Polite, factual, invoice attached again.

  4. Second reminder a week later

    Same tone, and ask whether there is a problem with the invoice — sometimes there is, and nobody told you.

  5. Then telephone

    Accounts payable, not your contact. Email is easy to leave unread; a call is not.

  6. Issue a receipt when it is paid

    See the receipt maker guide.

When it goes quiet

Keep every message factual and dated, and keep chasing on a schedule rather than by mood. If an invoice stays unpaid well beyond terms, escalate in writing with a clear deadline before considering formal recovery. Most disputes are resolved long before that, usually because the invoice was missing a PO number or sitting with someone on leave.

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Questions

Should I email the invoice as a PDF or in the body?

Attach a PDF. The email body is not filed, cannot be forwarded to accounts cleanly and is easy to alter. Summarise the key figures in the body and attach the document.

What should the invoice email subject line say?

The invoice number, your business name, the amount and the due date. It makes the email findable months later by anyone searching.

How soon should I follow up on an unpaid invoice?

A short reminder two or three days after the due date, another a week later, then a phone call to accounts payable. Consistency matters more than tone.

Can I send an invoice by WhatsApp?

Yes, and it is normal for domestic and trade work. Send the PDF file rather than a screenshot so the customer can forward it to their accountant.

Keep reading

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