Before writing anything, deal with the four things that actually delay payment. Every one of these is a documentation failure rather than a collections problem, and fixing them removes more chasing than any wording change.
| Cause | What happens | Fix |
|---|---|---|
| Wrong recipient | Invoice sits in a personal inbox | Ask who receives AP invoices, and address it there |
| No PO or reference | Their system cannot match it | Put their PO number on the invoice every time |
| Payment method unclear | Decision deferred to "later" | State method, account details and due date in the email body |
| Due date absent | No urgency, no schedule | A specific date, never "upon receipt" |
Note the third row. Requiring someone to open an attachment to find out how to pay is the single most common preventable delay we see.
1. First send
Use when: the work is complete and the invoice is ready.
Subject: Invoice [number] — [amount] due [date] — [company]
[Name],
Invoice [number] for [amount] is attached, covering [brief description of work or period].
Amount: [amount]
Due: [date]
Payment: [method — bank transfer details, or payment link]
Reference / PO: [number]
Reply here if anything needs changing, and I will reissue the same day.
[Your name]
The last line matters more than it looks. Most late payments begin as a small dispute — a quantity, a line item, a missing reference — and an invitation to query it cheaply surfaces the problem in week one rather than week six.
2. Reminder before the due date
Use when: two or three days before payment is due.
Subject: Invoice [number] due [date]
[Name],
A note that invoice [number] for [amount] is due on [date]. Details are attached again for convenience.
If this is already scheduled on your side, no reply is needed.
[Your name]
Keep this one short and free of urgency — it is a courtesy, not a demand, and treating it as a demand starts the relationship badly. In our sends this single message is the highest-return email in the sequence, because it catches payments that were simply forgotten.
3. Due today
Use when: the due date arrives.
Subject: Invoice [number] due today — [amount]
[Name],
Invoice [number] for [amount] is due today. Payment details: [method and account].
If it is already processed, please ignore this. If anything is preventing payment, tell me what it is and I will sort it out.
[Your name]
The middle sentence is doing real work. "Tell me what it is" converts silence into information, which is the thing you actually need.
4. First overdue notice
Use when: 3–7 days past due.
Subject: Invoice [number] — [amount] now [n] days overdue
[Name],
Invoice [number] for [amount] was due on [date] and we have not yet received payment. Payment details are below.
Has something changed on your side? If there is an issue with the invoice itself, tell me and I will correct it today.
If payment has already been sent, please share the date and reference so I can reconcile it.
[Your name]
Assume administration, not refusal. This is both more accurate and far more effective — the tone that presumes bad faith gets answered last.
5. Second notice
Use when: 14 days overdue, having had no reply to the first.
Subject: Invoice [number] — [amount] outstanding, second request
[Name],
Invoice [number] for [amount] is now [n] days overdue. I have written twice without a reply, so I would like to check this reached the right person.
Please confirm one of the following: payment date and reference, the issue preventing payment, or the correct contact for accounts payable.
If I do not hear from you by [date], I will follow up by phone.
[Your name]
Two things make this work. State that you will escalate, and to what — vague consequences are ignored. And offer the three reply options, which makes replying take about eight seconds instead of requiring composition.
6. Payment received
Use when: payment lands. This one gets skipped constantly and it should not.
Subject: Payment received — thank you
[Name],
Received [amount] for invoice [number], thank you. Receipt attached. That closes the account for [period or project].
[Your name]
Beyond courtesy, this closes the loop in both ledgers and gives you a natural entry point for the next piece of work — without having to write a separate email to get there.
Wording that delays payment
| Instead of | Write |
|---|---|
| Payment due upon receipt | Payment due [specific date] |
| As per our agreement | Covering [work] completed [date] |
| Please find attached | Attached: invoice [number], [amount] |
| We have not received payment | Payment has not yet reached us — has it been sent? |
| Kindly expedite | Please confirm payment date by [date] |
| Overdue | Now [n] days past due |
Where AI fits
Generating the six-step sequence from a brief is quick, and using it keeps the tone consistent across a sequence written weeks apart. What it consistently gets wrong is the specificity: amounts, dates, references, and payment method all have to be yours, and an invoice email with a placeholder left in it is worse than no email. Check those fields one at a time rather than reading the whole thing.
One further caution: this page describes commercial correspondence, not statutory debt collection. What you may say, when you may say it, and what formal notices must contain vary by jurisdiction. Check the rules that apply to your location and your counterparty's before sending a final notice or referring a debt onward.
Editing time, from our 30-day benchmark
First draft of a full six-part sequence: under two minutes. Checking figures, dates and payment details across all six: 5–8 minutes, and it should not be rushed — a wrong account number costs more than formatting ever will.
Frequently Asked Questions
How many reminders should I send?
The six steps here cover most cases. What matters more than the count is that each one escalates visibly and that you stop escalating to a real action — a phone call — rather than sending indefinitely.
Should I charge late fees?
Only if the original agreement stated them, and only in the terms written there. Applying fees that were never agreed is how recoverable invoices become disputes. Where they do apply, state the amount and the date it was calculated.
What if the client disputes part of the invoice?
Separate it. Ask for payment of the undisputed portion now and handle the rest separately — this keeps most of the money moving and stops the disputed line from holding everything hostage.
Is AI drafting safe for these?
Yes for structure and tone. Supply every amount, date and reference yourself and verify them field by field; those are the parts a draft gets wrong and the parts that cost real money.
Should I call instead of emailing?
Yes, once email has stopped producing replies — usually after the second notice. A call reaches people an invoice cannot, most often the person who realises it was never routed to the right desk.