How to Send an Invoice (Email Templates Included)
The right file format, subject line, recipient and follow-up cadence for invoices that actually get processed by accounts payable.
Send a PDF, always
PDFs render identically on every device and cannot be edited accidentally. Never send a spreadsheet or word-processor file as your invoice of record. Those formats break layouts, invite accidental edits, and sometimes get blocked by corporate email filters.
Create the PDF from a proper template first. The invoice generator exports a clean file you can attach immediately.
Name the file properly
Use a pattern like Invoice-2026-0041-AcmeLtd.pdf. Accounts-payable teams handle hundreds of files a week; a descriptive name gets yours filed instead of lost in a pile of invoice(3).pdf downloads. Include the client name as they know themselves, not your internal nickname for them.
Send it to the right person
Ask for the accounts-payable address at kickoff, not after the work is done. CC your day-to-day contact so they can approve internally. If the client uses a portal, follow their portal rules and still keep a PDF copy for your records.
Wrong inbox is one of the top reasons "we never got it" appears three weeks late. Confirm receipt with a one-line ask if the invoice is large: "Please confirm it landed with AP."
Subject lines that get opened and filed
Put the invoice number, client name, and due date in the subject. Avoid cute marketing language. Examples:
Invoice 2026-0041 | Acme Ltd | due 14 Aug 2026Invoice 2026-0041 | £2,400 | PO 77821
When chasing, keep the same number visible: Reminder: invoice 2026-0041 due today.
Email template: first send
Subject: Invoice 2026-0041 | Acme Ltd | due 14 Aug 2026
Hi Sam,
Please find attached invoice 2026-0041 for £2,400 covering the August retainer. Payment is due by 14 August; bank details are on the invoice. PO 77821 is referenced on the PDF.
Happy to answer any questions from AP.
Thanks,
Alex
Email template: polite reminder
Subject: Reminder: invoice 2026-0041 due today
Hi Sam,
A quick reminder that invoice 2026-0041 (£2,400) is due today. I have re-attached it for convenience. If it is already scheduled, please ignore this note.
Thanks,
Alex
Email template: seven days overdue
Subject: Overdue: invoice 2026-0041 (£2,400)
Hi Sam,
Invoice 2026-0041 for £2,400 was due on 14 August and appears unpaid on our side. Could you confirm whether it is with AP or if anything is missing for approval? Happy to resend in another format if needed.
Thanks,
Alex
Email template: firm escalation
Subject: Action required: invoice 2026-0041 now 14 days overdue
Hi Sam,
Invoice 2026-0041 (£2,400) is now 14 days past due. Per our agreement, late balances may incur interest as stated on the invoice. Please confirm a payment date this week or connect me with the person who can.
I have re-attached the PDF. Once paid, I will send a receipt referencing this invoice number.
Thanks,
Alex
Escalating without burning the relationship
After 14 days overdue, reference your late-payment terms and ask for a specific payment date rather than a vague update. Escalate to the budget holder if your only contact is a project manager without payment authority. Remain factual: amounts, dates, attachments.
If you supply ongoing work, state when work will pause. Surprises damage trust; clear conditions usually accelerate payment.
Portals, shared inboxes and international sends
- Follow portal field requirements exactly (tax IDs, coding blocks).
- Do not rely on a Slack DM as the official send. Always email or portal.
- For international clients, mention currency and fee responsibility in the body as well as on the PDF.
Attachments, links, and security filters
Prefer attaching the PDF directly. Links to expiring downloads create support burden and sometimes trigger corporate security reviews. Keep file size reasonable: compressed logos beat multi-megabyte background images that bounce from mail servers.
If you must use a portal link, still attach the PDF when the system allows it, or confirm the portal entry number in the email so everyone can cross-reference.
CC, BCC, and thread discipline
CC the project contact; avoid huge CC lists that encourage nobody to act. Do not BCC people who later need to reply-all with approval. Invisible stakeholders create invisible delays. Start a clean email for the first send rather than burying the invoice under a long project thread where AP never looks.
When chasing, reply to your original send thread so history is visible, and re-attach the PDF every time. Assuming they still have the file is optimistic.
After-hours and time zones
Sending at the start of the client's business week often beats Friday evening drops that sit untouched. For international clients, aim for morning in their time zone. Timing will not fix a broken invoice, but it stops avoidable delay when everything else is correct.
Shared mailboxes and handoffs
When AP is a shared inbox, address the email to the mailbox and greet the team by role ("Hello Accounts Payable") while still CC'ing your champion. Ask for a ticket or reference number if they use one. Record that reference on your tracker so future chases cite it. Handoffs between AP staff are smoother when your subject line already contains the invoice number they search for.
After it is paid
Send a short thank-you and a receipt that references the invoice number. Mark your tracker paid the same day. For the difference between the two documents, see invoice vs receipt.
Create the PDF first with our generator, then use the templates above. Freelancers can pair this with the freelancer's invoice guide; teams should align with the small business invoicing guide.
Frequently asked questions
Can I send an invoice by text message or WhatsApp?
You can send a quick heads-up or a PDF by text or messaging app, and some small clients prefer it. For business clients, still email the PDF or upload it to their portal, because accounts teams need a formal copy they can file and approve. Messaging apps are hard to search later and are rarely treated as the official send.
Should I send an invoice before or after the work is done?
It depends on your agreement. Send deposit or retainer invoices before work begins, milestone invoices when each phase is signed off, and final invoices on the day you deliver. Sending promptly matters more than the exact moment, because every day you wait moves you into a later payment cycle. Agree the billing schedule in your quotation.
How do I confirm my client actually received the invoice?
For large invoices, ask in the email for a one-line confirmation that it reached accounts payable. If the client uses a supplier portal, check its status screen for receipt or approval. Email read receipts are unreliable because many systems block them. If you hear nothing within a few business days, send a short follow-up asking whether anything is needed for approval.
Is it unprofessional to send invoices from a personal Gmail address?
It is acceptable for many sole traders, but an address on your own domain looks more established and is less likely to be flagged as suspicious by corporate filters. Whatever address you use, keep it consistent so clients recognize genuine invoices. If you trade as a company, make sure the invoice shows the company's legal name, not just your personal name.
Can I send an invoice directly from the free invoice generator?
No. The generator creates and downloads your invoice as a PDF in your browser, but it does not send emails. Download the PDF, name it with the invoice number and client name, and attach it to an email from your own account, or upload it to the client's portal. Keeping sending in your own inbox also gives you a record of when it went.
Should I mail a paper invoice?
Only when a client specifically asks for one, which still happens with some government bodies, older firms and individual customers. Print from the same PDF you keep on file so both copies match, and consider including a tear-off remittance slip with the invoice number. Note the posting date in your tracker, and allow extra days for delivery before the due date.
What should I do if my invoice email bounces or goes to spam?
If it bounces, check the address with your contact and resend immediately, noting the original send date. To reduce spam filtering, use a plain subject line with the invoice number, keep the attachment small, avoid link-heavy emails and send from a consistent address. For important invoices, ask the client to confirm receipt rather than assuming it arrived.
How do I submit an invoice through a client's supplier portal?
Complete the client's supplier onboarding first, including bank and tax details, because portals often reject invoices from unregistered suppliers. Then enter the invoice exactly as the portal asks, matching the PO number, line amounts and tax to your PDF. Upload the PDF if the portal allows it, and record the portal reference number in your tracker.
Should I password-protect my invoice PDF?
Usually not. Password-protected PDFs often fail in accounts-payable tools that read invoices automatically, and staff may not have the password when your contact is away. Instead, send to the confirmed accounts-payable address and avoid putting sensitive personal data on the invoice. If a client's policy requires encryption, follow their preferred secure upload method.
What is a customer statement and when should I send one?
A customer statement lists all invoices, payments and credit notes for one client over a period, ending with the total balance owed. It is useful for clients with several open invoices, often sent monthly. A statement is not a replacement for invoices, but it helps both sides spot missing payments, duplicates or invoices that never arrived.
Invoice Creator Editorial Team
Guides on invoicing, cash flow and small-business finance from Invoice Creator, operated by Next Software Development Company. Content is reviewed for accuracy against the fields our own invoice generator produces.
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