Six reasons an invoice goes overdue, and the fix for each#
Before you write, check your own side. Half of these are visible from your outbox.
| What | How you can tell | The fix |
|---|---|---|
| It never reached AP | Sent only to your contact; no portal record | Resend to the AP inbox or portal, contact in Cc |
| No PO, or the wrong PO | Their guidelines need one; your invoice has none | Ask for the PO, reissue with it |
| The wrong legal entity | The SOW names a subsidiary; you billed the parent | Cancel and reissue to the right entity |
| Waiting on an approver | AP says "pending approval" | Ask your contact to approve, naming the system |
| One line is disputed | A question came back about hours or scope | Answer it; ask for the rest to be paid |
| Their cash or their process | Paperwork is right, no answer for weeks | Escalate to the person who signed |
Only the last one is about money. The first five are about information, and each has a fix you can send the same day.
An example, used in the letters below. A design agency’s invoice INV-0418 for $22,000, milestone 2 of SOW 1, PO 7710042, was due on Monday, November 2, 2026. Nothing has come in.
| What | Send on | To |
|---|---|---|
| 3 days late | Thu, Nov 5 | AP inbox, contact in Cc |
| 10 days late | Thu, Nov 12 | The AP person by name, contact in Cc |
| 30 days late | Wed, Dec 2 | The person who signed the SOW |
Past due invoice email, 3 days late: ask what is holding it#
Three days late is still a question, not a complaint. Assume a paperwork reason, and offer to fix it.
Overdue invoice, 3 days late
To the AP inbox, your contact in Cc. Reply in the thread of the original invoice. Attach the PDF again.
Hello,
Invoice [INV-0418] for [$22,000], for [milestone 2 of SOW 1], was due on [November 2] and we have not seen the payment yet.
Is something holding it on your side, an approval, the PO or the billing entity? If the invoice needs a change, tell me what and I will send a corrected one today.
The PDF is attached, and the payment link is here: [payment link].
Thank you,
[Your name], [Your firm]
10 days overdue: a named person and a payment date#
By day ten, an inbox is not enough. Find the name of the person who processes supplier invoices: your contact knows, or the reply to the first letter was signed by someone. Ask for the one fact you need, the date.
Overdue invoice, 10 days late
To the AP person by name, your contact in Cc.
Hi [AP person's name],
I am writing about invoice [INV-0418] for [$22,000], PO [7710042], due on [November 2] and now [10] days past due.
Could you tell me which payment run it is scheduled for? If it is not scheduled, what does it need from us?
[Contact's name], copied here, confirmed acceptance of [milestone 2] on [date], in case approval is the step that is missing.
Thank you,
[Your name]
30 days overdue: the person who signed, and a call#
At thirty days, the invoice has missed at least one full cycle, and the letter goes to the person who signed the SOW or owns the budget. It comes from you, the founder, in your own words: this is a conversation between the two people who made the deal.
If the MSA provides interest on late payment, mention it once, as a fact of the contract, with the section number. If it does not, do not invent a fee in the letter.
Overdue invoice, 30 days late
From the founder, to the person who signed the SOW. AP and your contact in Cc. Attach the invoice and the earlier thread.
Hi [Name],
I wanted to raise this with you directly. Invoice [INV-0418] for [$22,000], for [milestone 2], was due on [November 2] and is now 30 days past due. Our notes to AP on [November 5] and [November 12] have not brought a payment date.
Could you help me find out what is holding it, and when we can expect it? Under section [7.3] of our MSA, overdue amounts carry interest at [1% per month]; I would rather we did not get there.
If it would help, I can take 15 minutes on a call this week: [two or three times].
[Your name], [title], [Your firm]
The call is often what moves it. How to ask a client for payment has the words for it. If the call does not bring a date, the next letter is the final notice.
60 and 90 days past due: the final notice#
At 60 days past due, the next email is no longer a reminder. It is the final notice: one date to pay by, and the one step your contract allows if that date passes, such as pausing the work. At 90 days, if the final notice and a call have not brought a date, the choice is between a payment plan in writing, a collections agency and small claims court. The final notice for an unpaid invoice has the letter and the call before it.
Three letters for the special cases#
The PO is missing. Their AP rejected the invoice, or will, because it carries no PO. Ask your contact, who raises POs, not AP, who cannot.
Overdue because the PO is missing
To your contact. AP in Cc only if they raised the issue.
Hi [Name],
Your AP team cannot pay invoice [INV-0418] for [$22,000] without a purchase order. Could you raise one for [milestone 2 of SOW 1], or send me the PO number if it already exists?
As soon as I have it, I will reissue the invoice with the PO, the same day.
Thanks,
[Your name]
The wrong entity or recipient. Do not edit the invoice and resend it under the same number. Cancel it and issue a correct one, so their system holds one version.
Overdue because it went to the wrong entity
To the AP inbox, contact in Cc. Attach the new invoice.
Hello,
Invoice [INV-0418] was addressed to [Parent Inc.]; it should have gone to [Subsidiary LLC]. We have cancelled it.
The attached invoice [INV-0421] replaces it: the same work and amount, [$22,000], PO [7710042], addressed to [Subsidiary LLC]. The due date stays [November 2], as in the SOW.
Payment link: [payment link]. Sorry for the extra step.
[Your name]
Whether the due date stays or restarts depends on what caused the error. If yours, offer a new date. If theirs (they gave you the wrong entity), keep the original one, as above.
One line is disputed. Answer the question with the record: the timesheet they approved, the acceptance email. And ask for the rest.
Overdue because one line is disputed
To whoever raised the dispute, AP in Cc. Attach the record that answers it.
Hi [Name],
Thank you for the question about the [design QA] line, [$3,500]. [It covers the 28 hours in the timesheet you approved on October 16, attached.]
The other lines, [$18,500], are not in question. Could your team pay those now, and we settle the [design QA] line separately?
If you still see it differently, I am happy to talk it through: [two or three times].
[Your name]
Should an overdue invoice email mention interest or a late fee?#
In the U.S., mention interest only if the contract provides it, at the rate the contract states. A late fee printed on an invoice that the client never agreed to is a request, not a right. The wording that makes it a right goes into the MSA before signature: the late payment fee clause has it.
In the UK, the law adds it for you. When a business pays another business late, the supplier can claim statutory interest at 8% above the Bank of England base rate,1 and a fixed sum for the cost of recovering the debt: £40 for a debt under £1,000, £70 from £1,000 to £9,999.99, and £100 for £10,000 or more.2 If no payment date was agreed, the payment is late 30 days after the customer gets the invoice or the service is provided.3 A UK version of the 30-day line:
Under the Late Payment of Commercial Debts (Interest) Act 1998, we are entitled to statutory interest on this invoice at 8% above the Bank of England base rate from [the due date], and to fixed compensation of [£100]. We would prefer not to claim it, and will not if payment reaches us by [date].
Five rules for the tone#
- Facts first, feelings never. “Due on November 2, now 10 days past due” is enough. “Disappointed” is not needed.
- One ask per letter. What is holding it; which run; a call.
- No “per my last email”. Quote the date of your last email instead.
- Thank them when it arrives. One line. It is the first letter of the next invoice.
- Keep the project out of it. The work and the payment run on separate tracks until the final notice.
Set up past due invoice emails in Tommos#
Tommos (tommos.ai) is a CRM whose AI agents, the tommos, take a B2B inquiry to a signed contract. On the Sign plan, Tommo Closer writes the past due invoice emails of this page for you, on your schedule and in your words. Here is the setup, once, and what you see after it.
- 1
Connect Mercury
In Settings, Invoices, copy the address under “First, in Mercury, allow this address on the token”, allow it on your Mercury API token, then paste the token and press “Connect Mercury”. From then on Tommos reads each invoice’s status, so a paid invoice never gets a reminder.
- 2
Accept the payment schedule
When a deal is won, Tommo Closer reads the signed SOW and puts the payment schedule on a card: each amount, its date or event, its payment term. You accept it or change it. Each invoice then comes as a card with two presses, “Make the invoice” and “Send”.
- 3
Set when the reminders go
Open Tommo Closer, the job “Get the deal paid”, its Letter. Under “When it reminds of an unpaid invoice” set “First, days after the due date” (3 by default), “Then every, days” (7) and “At most” (3). The defaults give reminders 3, 10 and 17 days late; the 30-day letter of this page, from the founder to the person who signed, stays yours.
- 4
Tell it how to write them
On the same page, in “How this job takes this act, in your words”, write the rules of this article the way you would brief a new colleague: the first reminder asks what is holding the invoice, the second goes to a named AP person with your contact in Cc, every one carries the invoice number, the PO and the payment link, and a late fee is named only when the contract has one.
- 5
Decide each reminder on a card
When an invoice is 3 days past due, the reminder waits on a card on your phone, written from the deal’s record. Send it, change a line, or skip it. A reminder never goes to a client on its own: one press sends it, and nobody has to remember the date. Tommo learns from what you change. After the last reminder, a person gets a task: the final notice or the call is your decision.
If the client objects to an invoice, Tommo answers from the record of the deal. If the invoice must change, one card cancels it and makes the correct one, as in the wrong-entity letter above.
Questions about overdue invoice emails#
- What should an overdue invoice email say?
- The invoice number, the PO, the amount, the due date and how many days past due it is, then one question: what is holding it, or which payment run it is in. Attach the invoice and give the payment link. Offer to fix any paperwork the same day.
- What is the difference between past due and overdue?
- None in practice: both mean the due date has passed and the invoice is unpaid. Some firms say "past due" in the first letters, as the softer word.
- How often should I follow up on an overdue invoice?
- Three days after the due date, then about ten, then thirty, each letter to a person one step higher. After that, a final notice with a date.
- Can I charge interest on an overdue invoice?
- In the U.S., if the contract provides it, at the rate it states, within your state's limits. In the UK, a business can claim statutory interest at 8% above the Bank of England base rate on a late payment from another business, plus a fixed sum of £40, £70 or £100.
- What if the client says they never got the invoice?
- Resend it the same day to the AP inbox or portal, with your contact in Cc, and ask them to confirm it is logged against the PO. Keep the original due date if it went to the address they gave you.
- Should I offer a payment plan on an overdue invoice?
- When the client says the money is tight, yes: two or three dated payments, in writing, beat a fourth reminder. Keep the payment plan short, name each date and amount, and say the full balance falls due at once if a payment is missed.
- What if the invoice is still unpaid after 30 days?
- Send a final notice with one date to pay by and one step your contract allows, such as pausing the work, then call the person who signed. A collections agency or a small claims court is a decision about the client relationship, and it comes only after that.
- What if they dispute part of the invoice?
- Answer the disputed line from the record, such as an approved timesheet or an acceptance email, and ask them to pay the undisputed lines by the due date. A dispute over one line should not hold the rest.
Key takeaways#
- Find out why the invoice is late before you chase it: five of six reasons are paperwork.
- 3 days late, ask AP what is holding it. 10 days, ask a named person for the run. 30 days, the founder writes to the person who signed.
- A missing PO goes to your contact; a wrong entity gets a new invoice, not an edit.
- Ask for the undisputed part to be paid while one line is discussed.
- Mention interest only when the contract, or UK law, gives it to you.
This is not legal advice. It comes from practice; for a large unpaid amount, an hour of a lawyer’s time is worth it.
Sources#
- GOV.UK, “Late commercial payments: charging interest”, read Oct 15, 2026
- GOV.UK, “Late commercial payments: claim debt recovery costs”, read Oct 15, 2026
- GOV.UK, “Late commercial payments: charging interest and debt recovery”, read Oct 15, 2026
Read next
- Payment reminder email: three templates before the due dateThe receipt check, the week-before note and the due-date line, with subject lines to copy.
- Final notice for an unpaid invoiceWhat the last letter may say, the call before it, the notice that pauses the work, and the UK letter before claim.
- How to get clients to pay on timeThe eight steps from the signed SOW to the money, the vendor setup email and the invoice checklist.