Last updated November 6, 2026
General information, not tax or legal advice. The rules depend on your country and your situation, so check anything with a tax or legal consequence with your accountant.
An invoice email clients can act on puts four facts in the first two lines: the invoice number, the amount, the due date and how to pay. Attach the invoice as a PDF, name the file clearly, send it to whoever approves payments, and write a subject line that can still be found by searching six weeks later.
The person reading it may have never heard of you. Write for them rather than for the contact you've been talking to.
What should an invoice email subject line say?
An invoice email subject line should say the word "invoice", the number, your business name and, if you have room, the amount and due date, because that's what someone will search for when the payment run comes round.
| Weak | Better | Why |
|---|---|---|
| Invoice | Invoice INV-2026-0042 from Harbour Signs: €2,304.00 due 28 April | Findable, and answers the first question without opening it |
| Invoice attached | Invoice INV-2026-0042, PO 5518, Harbour Signs | Accounts teams often match on the order number |
| March | March retainer: invoice INV-2026-0061 from Harbour Signs | "March" alone won't turn up in a search |
Standard invoice email template
The standard invoice email works for any routine invoice to a client who already knows you. Swap the bracketed details.
Subject: Invoice [number] from [your business]: [amount] due [due date]
Hello [name],
Invoice [number] for [what it covers] is attached. The total is [amount] including VAT, due by [due date].
Please pay by bank transfer to [account name], IBAN [IBAN], using [number] as the reference.
If anything doesn't match what you expected, reply to this email and I'll sort it out.
Thanks, [your name]
The line inviting a query matters more than it looks. A problem raised today costs you a day. The same problem raised on the due date costs you the whole payment term, and you start over.
Email for a first invoice to a new client
An email for a first invoice should also confirm the paperwork, because this is when a wrong address or a missing supplier record comes to light.
Subject: First invoice from [your business]: [number], [amount] due [due date]
Hello [name],
Here is our first invoice, [number], for [what it covers]: [amount] including VAT, due by [due date]. Payment details are on the PDF.
Could you confirm two things? That this is the right address for invoices, and that nothing else is needed to pay it, such as a purchase order number or a supplier form. If it should go to someone else, please tell me who and I'll send it straight on.
Thanks, [your name]
Email to an accounts inbox with a purchase order
An email to an accounts inbox should lead with the purchase order number, because that's what the reader will match against, and they won't know your contact's project.
Subject: Invoice [number], PO [order number], [your business], [amount]
Hello,
Please find invoice [number] attached, raised against purchase order [order number] from [contact's name].
Amount: [amount] including VAT. Due date: [due date]. Our details and bank account are on the invoice.
Please let me know if you need anything else to process it.
Kind regards, [your name]
Copy your contact, so they know it arrived and can approve it. If the customer asks for invoices through a portal, use the portal, because an emailed copy may simply be ignored.
Email for a deposit invoice
An email for a deposit invoice should say what happens once it's paid, since a client who can see what the payment starts has a reason to pay it promptly. The deposit and final payment guide covers how to bill it.
Subject: Deposit invoice [number]: [amount] to confirm [job]
Hello [name],
Thanks for accepting our quote. Invoice [number] for the [percentage]% deposit is attached: [amount] including VAT, due by [due date].
Once it's paid, we'll book [start of work]. The balance of [balance] will be invoiced on completion, as set out in the quote.
Thanks, [your name]
Email for a monthly invoice
An email for a monthly invoice can be very short, because nothing should have changed. Say so, and flag it clearly if something has.
Subject: [Month] invoice [number] from [your business]: [amount] due [due date]
Hello [name],
Your [month] invoice is attached: [number], for [amount] including VAT, due by [due date]. Same as last month, with no changes.
Thanks, [your name]
Email when a client says the invoice never arrived
An email re-sending an invoice should keep the original number and dates, because this is a copy and not a new bill. Don't reset the due date unless you've agreed to.
Subject: Copy of invoice [number] from [your business], due [due date]
Hello [name],
Sorry you didn't receive this. Here is a copy of invoice [number], issued on [issue date], for [amount], due by [due date].
Could you confirm it has reached you this time, and whether another address should have it?
Thanks, [your name]
Email for a corrected invoice
An email for a corrected invoice has to say which number is cancelled and which replaces it, or the customer may pay both or neither.
Subject: Corrected invoice [new number] replaces [old number]
Hello [name],
We've found an error on invoice [old number]: [what was wrong]. That invoice is now cancelled, so please disregard it.
The corrected invoice, [new number], is attached, for [amount] including VAT, due by [due date].
Sorry for the extra paperwork.
Thanks, [your name]
Should bank details go in the invoice email?
Bank details should go on the invoice PDF and can go in the email too, but never change them by email alone. Criminals send lookalike invoices with altered account numbers, so a change of bank details is exactly what a careful accounts team will distrust. If your account changes, phone your contacts as well, and send this:
Our bank account changes on [date]. I'll phone you to confirm the new details before your next payment. If you receive a change of account from us that I haven't confirmed by phone, please treat it as suspicious and call me on the number you already have for us.
Why do clients ignore invoice emails?
Clients ignore invoice emails mostly because the email doesn't reach the person who pays, or doesn't give them what they need to act.
- Going only to your contact, who can't release money and has other things on.
- A vague filename.
invoice.pdfis lost among dozens of others. Put the invoice number in the name. - A link instead of an attachment. An accounts team wants a file it can keep, and many block unknown links.
- A no-reply address. A query that bounces becomes a reason not to pay.
- Hiding the amount in the PDF. Someone clearing their inbox wants to see what you're asking for without opening anything.
If the due date passes, switch to the overdue reminder sequence.
Sending invoice emails from ERPFlow
Send via email on an invoice sends a fixed email. The subject reads "Invoice INV-2026-0042 from Your Business". The body greets the customer and gives the invoice number, issue date, due date and total, and the PDF is attached, with your bank details on it. Replies go to the email address in your business settings. The email and PDF use the invoice's language, any of 19.
The wording can't be edited, and the email goes to one address, filled in from the customer record. So ERPFlow's own email can't carry the templates above. To use them, choose Mark as issued without sending email, then Download PDF, send it from your own mailbox, and use Mark as sent so the invoice records its delivery.
Each email ERPFlow sends is recorded as the invoice's delivery and in the activity log, so you can check rather than guess when a client says nothing arrived. An email that fails leaves the invoice issued and not sent, and the Not sent filter lists what still has to go out. Emailing a paid invoice again says it has been paid in full, and a voided one says no payment is due. Recurring invoices can email each run the same way, with the same fixed wording.