Unpaid invoices: How to write past due invoice emails

Chasing down unpaid invoices shouldn’t be on your to-do list. A client misses a deadline, the payment doesn’t come through, and suddenly your team is stuck sending reminders, following up, and trying to figure out when (or if) the invoice will be settled. It’s a drain on time and cash flow.

‍

But the right approach to past-due invoice emails can make all the difference. Clear, professional follow-ups—sent at the right time—help businesses collect payments faster without straining client relationships.

‍

Let’s break down how to write effective past-due invoice emails, including what to say, when to send them, and how automation can take the manual effort off your plate.

What is an unpaid invoice?

An unpaid invoice is any bill that hasn’t been settled by the due date. Late payments, disputes, or a client’s financial difficulties can all lead to unpaid invoices—and if left unresolved, they can disrupt cash flow and slow down business operations.

‍

Common reasons invoices go unpaid are:

• Unclear payment terms: Vague or inconsistent terms create confusion and lead to delays.
• Client cash flow issues: Some customers push back payments due to financial struggles.
• Invoice errors: Missing details or incorrect amounts can cause disputes.
• Delayed invoicing: The later you send an invoice, the less urgency the client feels to pay it.
• Lack of follow-ups: Without reminders, invoices get overlooked or deprioritized.

How do unpaid invoices hurt businesses?

Unpaid invoices tie up cash that businesses rely on for payroll, operating costs, and growth investments. When payments don’t come in on time, companies may struggle with cash flow shortages, spend more time chasing payments, or even resort to expensive financing to fill the gaps.

‍

Over time, late payments can strain supplier relationships, make revenue forecasting difficult, and lead to costly write-offs that eat into profitability.

Are unpaid invoices the same as outstanding invoices?

Not exactly. An unpaid invoice is any invoice that hasn’t been paid—but that doesn’t always mean it’s overdue. An outstanding invoice is a broader category that includes both unpaid invoices that are still within the payment window and those that are past due.

‍

In short:

• Outstanding invoice: Any invoice that has been issued but not yet paid, whether it is still within the payment terms or overdue.
• Unpaid invoice: An outstanding invoice that has exceeded its due date and remains unpaid.

How to write past due invoice emails: 5 examples to get you started

Here are different email templates based on the level of urgency:

1. Initial reminder email (One week before due date)

Subject: Friendly Reminder: Invoice [#Invoice Number] Due on [Due Date]

‍

Dear [Client’s Name],

‍

We're hope you're doing well. Just a quick reminder that invoice [#Invoice Number] for [Invoice Amount] is due on [Due Date].

‍

For easy access, we've attached the invoice to this email. Please let us know if you have any questions or need any details.

‍

We appreciate your timely payment and your continued business. Let us know if there’s anything we can assist with.

‍

Best,
[Your Name]
[Your Company Name]
[Your Contact Information]

2. “Payment due today” email

Subject: Payment Reminder: Invoice [#Invoice Number] Due Today

‍

Dear [Client’s Name],

‍

We hope you're doing well. Just a quick reminder that invoice [#Invoice Number] for [Invoice Amount] is due today, [Due Date].

‍

For your convenience, we've attached the invoice again. Please ensure payment is processed today to avoid any delays. If payment has already been made, kindly disregard this message—but we’d appreciate a confirmation for our records.

‍

Let us know if you have any questions or need any assistance. We appreciate your prompt attention and your continued business.

‍

Best,
[Your Name]
[Your Company Name]
[Your Contact Information]

3. First overdue notice (30 days past due)

Subject: Urgent: Invoice [#Invoice Number] Now 30 Days Overdue

‍

Dear [Client’s Name],

‍

We hope this message finds you well. We wanted to follow up regarding invoice [#Invoice Number] for [Invoice Amount], which is now 30 days overdue.

‍

A late fee of [Late Fee Amount] has been added to your balance. Please arrange payment as soon as possible to prevent further delays. If you’ve already processed the payment, kindly send us a confirmation.

‍

If you're experiencing financial difficulties, let us know—we're happy to discuss potential payment arrangements. Please reach out at your earliest convenience.

‍

We appreciate your prompt attention to this matter.

‍

Best,
[Your Name]
[Your Company Name]
[Your Contact Information]

4. Second overdue notice: 60 days past due

Subject: Immediate Action Required: Invoice [#Invoice Number] 60 Days Overdue

‍

Dear [Client’s Name],

‍

We’re reaching out regarding invoice [#Invoice Number] for [Invoice Amount], which is now 60 days overdue. An additional late fee of [Late Fee Amount] has been applied to your balance.

‍

To avoid further action, please process payment immediately. If payment has already been made, kindly send us the transaction details for confirmation.

‍

If you need to discuss payment options, please reach out as soon as possible. We’re here to help find a resolution.

‍

We appreciate your prompt attention to this matter.

‍

Best,
[Your Name]
[Your Company Name]
[Your Contact Information]

5. Final notice before escalation: 90 days past due

Subject: Final Notice: Immediate Payment Required for Invoice [#Invoice Number]

‍

Dear [Client’s Name],

‍

Despite multiple reminders, invoice [#Invoice Number] for [Invoice Amount] remains unpaid and is now 90 days overdue. An additional late fee of [Late Fee Amount] has been applied to your balance.

‍

Immediate payment is required to prevent further action, which may include service suspension or referral to a collection agency. If payment has already been made, please provide transaction details as soon as possible.

‍

If there are any outstanding issues preventing payment, please contact us immediately to discuss resolution options.

‍

This is the final notice before escalation. We appreciate your urgent attention to this matter.

‍

Best,
[Your Name]
[Your Company Name]
[Your Contact Information]

5 simple strategies for collecting unpaid invoices

Collecting unpaid invoices requires immediate action to prevent delays from disrupting cash flow. While similar to handling outstanding invoices, collecting overdue invoices requires proactive intervention to prevent payment delays from becoming chronic cash flow issues.

‍

Below are invoicing best practices to recover unpaid invoices efficiently:

1. Send payment reminders promptly: As soon as an invoice is overdue, send a clear, professional reminder.
2. Engage in direct communication: If reminders fail, call or email to identify payment obstacles. Clients may need clarifications or face temporary financial setbacks.
3. Offer alternative payment methods: Faster payment options can resolve unpaid invoices more quickly. Multiple ways to pay reduce friction and speed up settlements.
4. Enforce late fees and payment policies: Clearly stated late fees encourage on-time payments. Ensure penalties are outlined in contracts and reinforced in reminders.
5. Determine when to escalate: If multiple attempts fail, assess whether to involve collections, adjust terms, or take legal action to prevent long-term revenue loss.

How automation streamlines unpaid invoice collection

Manual collections are time-consuming and easy to fall behind on. Automating invoice management helps businesses stay ahead of late payments with:

• Scheduled invoicing: Ensure invoices go out on time, every time.
• Automated payment reminders: Reduce the need for manual follow-ups.
• Online payment options: Make it easier for clients to pay quickly and securely.
• Real-time tracking: Monitor overdue invoices and identify patterns before they become a problem.
• Accounting system integrations: Keep records accurate and simplify reconciliation.

‍

With the right tools in place, businesses can reduce unpaid invoices, accelerate collections, and improve cash flow without adding more manual work.

Streamline your invoice management with Ramp

For businesses managing a high volume of transactions, automating invoice processing can significantly cut down the time spent on invoice matching, data entry, and approvals. Ramp’s finance platform simplifies automation, making it easy to process invoices faster and more efficiently.

‍

With Ramp, routine tasks like coding, verification, and approvals are automated, giving your AP team more time to focus on high-value work. Don’t take it from us, take it from clients like Quora who were able to reduce invoice processing time to just 1–2 minutes per bill with Ramp.

‍

Imagine what your team could accomplish with that kind of time savings. Explore Ramp’s invoice management software to get started.