What is an overdue invoice?

An overdue invoice is an invoice that has not been paid by its due date. The due date may come from your contract, payment terms or the invoice itself.

When should I send a payment reminder?

Many businesses send a friendly reminder shortly before the due date, then a polite follow-up after the invoice becomes overdue. The right timing depends on your client relationship and agreement.

Can I charge a late fee?

Late fees depend on your contract and local law. Check the agreement and rules in your jurisdiction before adding fees.

How do I calculate late payment interest?

A common estimate is invoice amount times annual interest rate divided by 365, multiplied by days overdue. This tool uses that formula when you enter a rate.

What should an invoice reminder include?

Include the invoice number, amount, due date, days overdue if relevant, a clear payment request and a professional next step.

Does this tool store my invoice data?

No. The calculator runs in your browser and does not store invoice data in a database or account.

Free invoice utility

Calculate overdue invoice fees and generate a payment reminder.

Q: Is this legal advice?

No. This tool provides general calculations and communication templates only. It does not provide legal, tax or financial advice.

Free tool for freelancers, agencies and small businesses. No signup required.

Open calculator View templates Create reminder

Your invoice data is processed locally in your browser and is not stored.

Calculator$1,037.53

Days

Rate

Fee

$15

Your invoice data is processed locally in your browser and is not stored.

Overdue invoice calculator

Enter the invoice details to estimate overdue days, optional interest and late fees.

Invoice amountCurrency

Invoice datePayment terms

Due dateToday date

Country suggestion for interest and late fee

Annual interest rate (%) (Optional)Flat late fee (Optional)

Client or company name (Optional)Invoice number (Optional)

Source notes are provided for context. Manually entered interest or fees should be used only if contractually agreed or legally checked.

Result

Not overdue

Days until due: 30
Original invoice amount: $1,000.00
Estimated interest: $0.00
Flat late fee: $0.00

Estimated total due$1,000.00

Suggested next action

Send a friendly reminder shortly before the due date.

Payment reminder generator

Generate a professional message using the invoice details above.

ToneRelationship

Salutation

Email subject

Email body

Dear Sir or Madam,

I hope your week is going well. I am following up on your invoice. It is currently 0 days overdue. The outstanding invoice amount is $1,000.00.

Please let me know the expected payment date or if you need another copy of the invoice.

Best regards,

Short message

Dear Sir or Madam, your invoice is 0 days overdue. The outstanding invoice amount is $1,000.00. Could you confirm the expected payment date?

Create reminder

Create a local reminder email and calendar event from the calculator details. No reminder data is stored or sent by this website.

Reminder titleReminder dateSend reminder to

Email preview

Reminder: Invoice

This is a reminder for Invoice.

Reminder date: Jun 17, 2026

Please check the invoice status and follow up if needed.

The email opens in your mail app via a mailto link. This site does not send or store the reminder.

A calmer way to follow up on late invoices

The calculator gives you numbers, but the next step should still feel human. Use a short, repeatable process before mentioning interest or fees.

Check the basics

Confirm invoice number, amount, due date and payment terms before writing.

Start clear

Send a friendly note first, especially when the client relationship matters.

Add context

Mention days overdue, agreed terms and the exact amount if the invoice remains unpaid.

Escalate carefully

Use firmer wording only after the earlier reminders were documented.

Payment reminder templates

Localized examples you can adapt before sending. Keep the tone professional and check your agreement before mentioning fees.

Friendly payment reminder email

Hi Acme,

I hope you are well. This is a friendly reminder that invoice INV-1042 for $1,000.00 is due on May 30, 2026. Please let me know if payment is already on its way.

Thank you.

Polite overdue invoice reminder

Hi Acme,

I am following up on invoice INV-1042 for $1,000.00. It appears to be overdue. Could you confirm when payment will be made?

Best regards.

Firm payment reminder

Hi Acme,

Invoice INV-1042 for $1,000.00 is now overdue. Please arrange payment as soon as possible or send a confirmed payment date.

Regards.

Final notice for unpaid invoice

Hi Acme,

This is a final notice for unpaid invoice INV-1042. Please make payment promptly or contact us with a confirmed payment plan.

Regards.

Practical invoice follow-up guides

Short guides that explain the decisions behind the calculator without turning the page into a textbook.

Payment reminder guide

Learn when to send friendly, polite, firm and final payment reminders without damaging client relationships.

Read guide

Late payment interest

Understand how late payment interest is estimated and why contract terms and local law matter.

Read guide

Follow-up checklist

A compact checklist for following up on overdue invoices with clear records and professional wording.

Read guide

Frequently asked questions

Important notice

This tool provides general calculations and communication templates only. It does not provide legal, tax or financial advice. Always check your contract and local laws before charging late fees or interest.

Your invoice data is processed locally in your browser and is not stored.