Late payments are one of the biggest challenges for small businesses. You’ve sent the invoice, provided the product or service, and waited. But when the payment is due — nothing arrives.
No matter if it has been a few days or several weeks, knowing how to follow up on an unpaid invoice can help. It can keep your relationship with your client professional. It can also help you avoid awkward talks and protect your cash flow.
In this guide, we’ll walk through:
- What counts as a past due invoice
- How to follow up at each stage
- Sample payment reminder emails
- Tips to reduce delay payments
- When to escalate — and how
Let’s get started.
What Is a Past Due Invoice?
A past due invoice is one that has not been paid by the invoice due date listed on the original invoice. Once that date passes, the invoice is considered overdue — even if it’s just by a single day.
Many businesses offer grace periods, but technically, payment is due on the specified date. After that, it’s up to the business to begin collecting payments and sending reminders to ensure they’re paid on time.
Why Is It Crucial to Follow Up on an Unpaid Invoice?
Unpaid invoices directly affect your business’s cash flow. When you don’t receive payments on time:
- It becomes harder to manage expenses and payroll
- You lose track of income projections
- You may struggle with your own vendor payments
Late or missed payments also cost you valuable time — especially if you’re chasing multiple clients to pay.
Establishing a clear and professional follow-up process helps you:
- Collect payments faster
- Reduce the number of days invoices remain unpaid
- Build trust and set boundaries with clients
- Maintain positive relationships
Review Past Due Invoices
Before following up, double-check:
- The client’s contact information
- The terms listed in the original invoice (including due date)
- Whether a payment has already been received but not yet recorded
- Any previous communication about the delay
Sometimes the issue is a missed email, a forgotten bank transfer, or a mix-up on the client’s end. Reviewing these details saves time and makes your message more effective.
Send an Overdue Invoice Notice via Email
Start with a courteous payment reminder email. Keep the tone professional and friendly. Assume the delay is unintentional unless there’s a pattern of non-payment.
Be sure to include:
- The invoice number and due date
- The outstanding balance
- A copy or link to the original invoice
- Accepted payment methods (e.g. credit card payments, bank accounts)
Still unsure how to word your reminder? Check out our guide on: How to Write an Effective Collection Notice
Escalate the Follow-Up if Necessary
If your first message goes unanswered, or the invoice remains unpaid after 1–2 weeks, it’s time to send a stronger follow-up. You can:
- Send a second, more direct email
- Call the client directly
- CC another contact or department (e.g. Accounts Payable)
Maintain a professional tone, but make it clear that collecting payment is a priority.
Personalize the Final Communication
If the invoice is still unpaid after 30 or 60 days, consider sending a final notice. This message should:
- Recap the full history of communication
- Restate the total amount due
- Include a firm deadline
- Mention any next steps, such as late fees or legal action
Being clear and calm helps protect your business. You’re giving the client one last opportunity to resolve the issue without conflict.
Take Legal Action
Legal action should always be a last resort, but sometimes it’s the only way to collect an outstanding balance. This might involve:
- Hiring a collections agency
- Filing a claim in small claims court
- Working with a lawyer to draft a demand letter
Be sure to keep records of all communication and invoice documents in case they’re needed in court.
Past Due Invoice Email Templates
Day 1: The Payment Due Date
Subject: Friendly reminder: Invoice #12345 due today
Hi [Client Name],
Just a reminder that invoice #12345 for [product or service] is due today. Please let us know once the payment is submitted. If you’ve already sent it, feel free to disregard this message!
Thanks so much, [Your Name]
Day 15: Two Weeks Late
Subject: Follow-up: Invoice #12345 is overdue
Hi [Client Name],
We noticed invoice #12345 is now two weeks past due. Please take a moment to check on the status. You’ll find a copy of the invoice attached.
If there’s anything we can do to assist, just let us know.
Best, [Your Name]
Day 30: One Month Late
Subject: Payment needed: Invoice #12345 is 30 days overdue
Hi [Client Name],
Our records show invoice #12345 is still unpaid. At this point, we’d greatly appreciate an update.
The outstanding balance is [$XXX.XX], and we’ve attached the invoice again for reference.
Please let us know your expected payment date.
Thank you, [Your Name]
Day 60: Two Months Late
Subject: Final Notice: Invoice #12345
Hi [Client Name],
Despite several reminders, invoice #12345 remains unpaid. This is our final notice before we begin further action to collect payment.
Please respond within 5 business days to avoid additional fees or steps.
Regards, [Your Name]
For more templates, explore Invoice Fly’s
Unpaid Invoice Email Escalation
Following up on unpaid invoices doesn’t have to feel awkward — but it should be structured. Using a tiered approach helps guide the client gently at first, then becomes more assertive as the delay continues. Here’s a breakdown of how to escalate communication effectively, without damaging your relationship or sounding aggressive.
1. The Reminder
This is your first follow-up, typically sent the day payment is due. Keep it light, polite, and helpful.
Tone: Friendly and casual.
Goal: Nudge the client to check their records or initiate the transfer.
Example: “Hi [Client], just a quick reminder that invoice #12345 is due today. Let us know if you need the payment link re-sent.”
2. The Nudge
If no payment is received within a week or two, it’s time to follow up again.
Tone: Slightly firmer, still respectful.
Goal: Reinforce urgency without applying pressure.
Example: “Hi [Client], we noticed invoice #12345 is still outstanding. Could you confirm if payment has been scheduled?”
3. Official Notice
At the 30-day mark, tone becomes more formal.
Tone: Professional and direct.
Goal: Signal that the situation is serious and payment is expected soon.
Example: “As of today, invoice #12345 is 30 days overdue. Please arrange payment or reply with an update by [specific date].”
4. The Direct Ask
Now’s the time for clarity. Ask directly for payment and suggest support options if needed.
Tone: Assertive but helpful.
Goal: Remove ambiguity and show you’re actively managing your billing process.
Example: “Please confirm your expected payment date. If there’s a problem on your end, we’re happy to work with you.”
5. The Final Notice
This message communicates the final opportunity to pay before legal or collection steps begin.
Tone: Firm and final, without sounding hostile.
Goal: Make consequences clear while giving a last chance to resolve it.
Example: “Despite several attempts, invoice #12345 remains unpaid. This is our final request before escalation. Please respond within 5 business days.”
Using this gradual approach helps you stay professional, build trust, and increase your chances of collecting payment. Most importantly, you are protecting your business long term.
Tips for Effective Overdue Invoice Follow-Up
1. Agree Upfront to a Preferred Invoice Payment Process
Set clear expectations in your contract or service agreement. Outline your invoice schedule, payment methods, and terms.
2. Clarify What Your Customer Is Paying for and When It’s Due
Every invoice should include:
- Itemized list of goods or services
- Contact information
- Payment terms and conditions
- Payment due date
3. Establish a Process for Following Up on Past Due Invoices
Create templates and automate payment reminder emails where possible. Stick to your follow-up timeline so no invoice slips through the cracks.
Key Takeaways
- Always remain professional and calm in your follow-up messages
- Use a timeline: Day 1, Day 15, Day 30, Day 60
- Make it easy for clients to pay by offering multiple options
- Document everything — especially for long term unpaid invoices
- Consider escalation only when necessary
With the right structure in place, following up on unpaid invoices becomes a simple part of doing business — not a stressful task.
Choose the Best Payment Setup for Your Business
To prevent delays, make it easy for clients to pay:
- Offer multiple payment methods (e.g. ACH, credit card payments)
- Use invoicing software to send invoices and track status
- Include clear instructions for how to pay
Looking to simplify the process? Try Invoice Fly’s Invoice Maker to automate your reminders, send professional invoices, and manage unpaid invoices with ease.
