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Letter template

Past Due Invoice Letter Template

Updated 2026-10-24

A past due invoice letter is a formal written notice telling a business customer that an invoice is unpaid after its due date. It lists the invoice number, original due date, days overdue, and balance, then asks for payment or a reply by a specific date. It is firmer than a friendly reminder but still professional, and it creates a written record if the account later goes to collections.

When to use this template

  • When a customer has acknowledged the invoice by phone but has not given a payment date, and you want the conversation confirmed in writing.
  • When an invoice is 15 to 30 days past due and a friendly reminder went unanswered.
  • When you need a dated written record of the balance for your files or for a future collection agency referral.
  • When the customer has several open invoices and you want to list them together in one statement.
  • When your contact has changed and you need to put the balance in front of the company's accounts payable department formally.

The template

{Your Company Name} {Your Address} {City, State ZIP} {Date} {Customer Contact Name} {Customer Company Name} {Customer Address} {City, State ZIP} Re: Past due invoice {Invoice Number}, account {Account Number} Dear {Customer Contact Name}, Our records show that the invoice below is now past due: Invoice number: {Invoice Number} Invoice date: {Invoice Date} Original due date: {Due Date} Days past due: {Days Past Due} Balance due: {Balance Due} We sent a reminder on {Reminder Date} and have not yet received payment or a response. We understand that invoices sometimes get delayed in approval, so we wanted to reach out directly. Please send payment of {Balance Due} by {Payment Deadline}. You can pay online at {Payment Link}, by ACH using the remittance details on the enclosed invoice, or by check payable to {Your Company Name} at the address above. Please include the invoice number with your payment. If you have already sent payment, please reply with the payment date and method so we can match it to your account. If there is a question about this invoice, or if you need to discuss timing, please contact me at {Your Phone Number} or {Your Email} before {Payment Deadline}. We would much rather work out a solution with you than let the balance grow older. Thank you for your prompt attention. Sincerely, {Your Name} {Your Title} {Your Company Name} Enclosure: Invoice {Invoice Number}

How to customize it

  • Set a specific payment deadline, usually 7 to 10 days from the letter date. A date gets more action than 'at your earliest convenience.'
  • If there are several open invoices, replace the single invoice block with a short table showing each invoice number, date, amount, and days past due, plus a total.
  • If your signed terms provide for late fees or interest, you may add one factual line stating the amount and the contract clause. Leave it out if your terms do not provide for it.
  • Address the letter to the accounts payable department as well as your usual contact if your contact has been unresponsive.
  • Send it by email with a PDF attached and keep a copy. For larger balances, also mail it so you have proof of delivery.
  • If the customer says they never received the invoice, resend it the same day with this letter attached, confirm the correct AP email address, and ask for confirmation of receipt. Reset the payment deadline if needed, but keep the original due date on record.

Mistakes to avoid

  • Do not threaten collections or legal action in the first past due letter unless you are truly ready to follow through. Empty threats weaken later notices.
  • Do not add fees or interest that are not in your written terms or invoice. Charging amounts you have no right to can create a dispute and hurt your claim.
  • Avoid vague balances. State the exact amount and how it was calculated so the customer cannot stall by asking for a breakdown.
  • Do not write in all caps, red text, or language that reads as angry. A calm, factual tone is more persuasive and looks better if the file is ever reviewed later.
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Frequently asked questions

How is a past due invoice letter different from a reminder?

A reminder is informal and assumes an oversight. A past due letter is a formal notice with a payment deadline and a full record of the balance, sent after the reminder has gone unanswered.

Can I charge interest on a past due business invoice?

Only if it is provided in your terms, such as a signed credit application, contract, or terms printed on the invoice, and the rate complies with your state's limits. If your terms are silent, do not add it.

Should I send the letter by mail or email?

Email is faster and usually enough. For balances that might end up in collections, also send a mailed copy so you have proof the customer received written notice.

How many days past due should an invoice be before I send this letter?

Many businesses send a formal past due letter once an invoice is 15 to 30 days late. Use the same timing for every customer so your process is consistent, and send it sooner for large balances or customers with a history of slow payment.

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Prepared by the Ironside Commercial Recovery collections team. General information, not legal advice. Have counsel review letters that reference legal action or statutory requirements.

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