What Is the Best Way to Follow Up on Unpaid Invoices?

Why unpaid invoices happen and why your follow-up matters

Unpaid invoices are one of the most common (and most frustrating) problems for freelancers, agencies, contractors, and small businesses. You do the work, you deliver the service or product, you send the invoice, and then… silence. Sometimes it’s accidental—your invoice gets buried in an inbox, the approver is on holiday, or the client’s accounts team needs a purchase order number you didn’t know about. Other times it’s a cash-flow issue on their side, or a lack of urgency because they assume you’ll wait indefinitely.

The best way to follow up on unpaid invoices is to be consistent, professional, and systematic. The goal isn’t to “nag” or create tension—it’s to make it easy for the customer to pay, remove friction, and set clear expectations. A structured follow-up process also protects your time and prevents overdue payments from turning into bad debt.

If you’re using a modern invoicing tool like invoice24, your follow-up becomes dramatically easier because you can issue invoices quickly, track due dates, send reminders, document communication, and keep everything in one place. That matters because the best follow-up strategy isn’t just one email—it's a repeatable workflow you can apply to every invoice without rewriting messages from scratch.

The “best way” in one sentence: a calm, staged process

Here’s the most effective approach in practice: follow up in stages—friendly reminder, due-date check-in, overdue notice, firm final reminder—while always providing a clear payment link, the invoice details, and a simple next step. You stay polite at the start, become more direct as the invoice ages, and escalate only when needed.

This staged approach works because it aligns with how most late invoices actually happen: the majority aren’t malicious—they’re delayed because of oversight, internal approval steps, or missing details. A gentle nudge solves most cases. For those that don’t resolve, your documented, consistent follow-up creates the paper trail you need to escalate confidently.

Set yourself up to get paid before you ever need to follow up

The follow-up process starts long before an invoice is overdue. The “best way” includes prevention, because a clean invoice and clear payment terms reduce the likelihood of late payments in the first place.

Send invoices promptly and consistently

The longer you wait to invoice, the longer you wait to get paid. Send the invoice immediately after delivery or at the agreed milestone. If you invoice on a schedule (weekly, biweekly, monthly), be consistent so clients come to expect it. A tool like invoice24 helps by keeping invoicing quick and repeatable, so you don’t procrastinate because it feels like admin work.

Make your invoice easy to approve

A surprising number of invoices go unpaid because they’re missing something required by the client’s accounts process. Reduce the chance of delays by including:

• A clear invoice number
• Correct client billing details (company name, address, VAT/tax numbers if applicable)
• A short description of the work delivered and the date range covered
• Your payment terms and due date
• Any purchase order (PO) number or reference they require
• A simple way to pay (bank details and/or online payment options)

With invoice24, you can standardize invoice templates so these details are always included, reducing preventable back-and-forth.

Use clear terms and a due date that creates urgency

“Net 30” is common in some industries, but if you’re a freelancer or small business, shorter terms can be healthier for cash flow. Whatever you choose, make it explicit: “Payment due within 7 days” or “Due on 15 March 2026.” A specific date often creates more urgency than vague wording.

Offer multiple payment methods

If paying you is hard, paying you will be slow. Reduce friction by allowing the most convenient payment options for your customers. Some clients prefer bank transfer, others prefer card. Even when you mainly accept bank transfers, providing a quick online option for smaller invoices can speed up payment substantially.

The ideal follow-up timeline (and why it works)

To follow up effectively, you need a timeline you can apply consistently. Below is a proven schedule you can adapt based on your typical payment terms. The idea is to remind early, follow up near the due date, and escalate after the due date if needed—without jumping straight to threats or legal language.

Day 0: Invoice sent

When you send the invoice, make sure it’s clearly marked as an invoice (not just an attachment with no context). Include the due date, total amount, and how to pay. In invoice24, you can keep customer details and invoice history organized, which makes sending invoices quick and consistent.

Day 3–7 (before due date): Friendly reminder

This reminder catches the “buried inbox” problem. It’s short, friendly, and assumes good intent. The best reminder includes the invoice number, amount, and due date—plus a clear payment link or instructions.

Tip: If you know the client typically pays later, you can time the reminder closer to the due date. If your terms are Net 7, send it around day 3–4. If Net 30, send it around day 14–21.

Due date: Due-today check-in

On the due date, a simple check-in can prevent the invoice from drifting into the “overdue” pile. Keep it polite and action-oriented: “Just a reminder it’s due today—let me know if you need anything to process it.”

1–3 days overdue: Overdue notice (still polite)

Now you shift from “reminder” to “overdue.” The tone is still professional, but you’re clearer. You’re no longer asking if they’ve seen it—you’re stating the status and asking for a payment date.

7–14 days overdue: Firm follow-up + consequences

If the invoice remains unpaid, it’s time to be more direct. You can reference your terms and mention late fees (if you have them in your contract) or the need to pause ongoing work until the account is brought current. Keep consequences factual, not emotional.

21–30+ days overdue: Final notice and escalation

If you still haven’t been paid, the best practice is to issue a final notice that sets a deadline. You can mention formal escalation such as debt collection, small claims court, or turning the matter over to your accountant or legal counsel. The key is to do this calmly and only after you’ve documented multiple attempts to resolve the issue.

Write follow-ups that get paid: what to include every time

Regardless of which stage you’re in, the most effective follow-ups include the same core elements. These reduce confusion and remove excuses for delay.

1) Clear subject line

A good subject line makes it obvious what the email is about. Examples include:

• “Reminder: Invoice #1042 due on 15 March 2026”
• “Overdue: Invoice #1042 (Payment requested)”
• “Final notice: Invoice #1042 – please confirm payment date”

2) Invoice details in the body

Always include the invoice number, amount, and due date, even if the invoice is attached. People forward emails internally and details get separated from attachments.

3) A simple way to pay

The fastest follow-ups provide a direct payment path. If you’re using invoice24, you can streamline this by keeping the invoice and payment instructions neatly accessible so the client can pay without emailing back for details.

4) One clear ask

Don’t overload the email. Ask for one action: “Please pay today,” or “Please confirm when payment will be made,” or “Please let me know if you need a revised invoice with a PO number.”

5) A professional, calm tone

Even when you’re frustrated, don’t show it. Late invoices often resolve faster when you stay businesslike. Aggressive language may feel satisfying, but it can slow payment by triggering defensiveness or avoidance.

Follow-up templates you can adapt

Below are sample follow-ups you can copy and adjust. You’ll get best results if you personalize them slightly (e.g., use the recipient’s name and reference the project). If you use invoice24, you can save versions of these messages and reuse them so follow-up becomes a workflow rather than a recurring writing task.

Template 1: Friendly reminder (before due date)

Hello [Name],

Just a quick reminder that invoice [#] for [amount] is due on [due date]. If you’ve already scheduled payment, please ignore this message.

If you need anything from me to process it (PO number, updated billing details, or a copy of the invoice), let me know and I’ll help right away.

Thanks,
[Your name]

Template 2: Due-today check-in

Hello [Name],

A quick note that invoice [#] for [amount] is due today ([due date]). Could you confirm when payment will be made?

Thanks,
[Your name]

Template 3: Overdue (1–3 days late)

Hello [Name],

Invoice [#] for [amount] was due on [due date] and is now overdue. Please arrange payment at your earliest convenience and let me know the expected payment date.

If there’s any issue with the invoice details, I can resolve it quickly—just tell me what’s needed.

Kind regards,
[Your name]

Template 4: Firm follow-up (7–14 days overdue)

Hello [Name],

I’m following up again regarding the overdue invoice [#] for [amount], originally due on [due date].

Please confirm the payment date by [specific date]. If payment has not been scheduled, I’ll need to pause further work/services until the account is brought up to date, in line with our terms.

Thanks for your prompt attention,
[Your name]

Template 5: Final notice

Hello [Name],

This is a final reminder that invoice [#] for [amount] remains unpaid, despite previous reminders. Payment was due on [due date].

Please make payment by [final deadline] or respond with a confirmed payment date. If I don’t hear back by then, I will proceed with formal escalation to recover the outstanding balance.

Sincerely,
[Your name]

Email is good, but the phone call often closes the loop

If emails aren’t getting a response, a short, polite phone call can be the fastest solution. Many people ignore emails when they feel overwhelmed. A call is harder to avoid and often reveals the real issue: “We need the PO number,” “Our approver is out this week,” or “Can you resend it to accounts@company.com?”

Keep it brief and friendly:

• Confirm they received the invoice
• Ask if anything is needed to process it
• Ask when payment is scheduled
• Thank them and follow up in writing with a summary

After the call, send an email recap. That recap becomes part of your documentation trail, which is valuable if the situation escalates later. If you manage invoices through invoice24, you can keep your invoice records tidy so you always know what was sent and when.

How to handle common excuses (without getting pulled into endless back-and-forth)

Late payers often rely on vague responses to buy time. Your job is to stay polite while moving the conversation toward a commitment: either a payment date or a clear correction needed to release payment.

“We didn’t receive the invoice.”

Reply with the invoice attached again and include the key details in the email body (invoice number, amount, due date). Ask them to confirm the correct accounts email address for future invoices. In invoice24, having customer records organized helps you avoid sending to outdated contacts.

“We’re waiting for approval.”

Ask who the approver is and when approval is expected. Then ask for a realistic payment date. The goal is to turn “waiting” into a timeline.

“Can you send it to our accounts department?”

Send it immediately, copy the original contact, and ask accounts to confirm receipt. Update the billing contact details so the next invoice goes to the right place.

“We have cash flow issues.”

Stay calm. Ask for a partial payment now and a payment plan for the remainder. If you have ongoing work, consider pausing until at least a portion is paid. Document everything clearly.

“We dispute the invoice.”

Ask for specifics. Many “disputes” are vague stalling tactics. If it’s legitimate, resolve it quickly and reissue the invoice if needed. If it’s not legitimate, refer back to the agreement and request payment by a set date.

Late fees, interest, and payment terms: use them strategically

Late fees can be helpful, but only if they’re included in your contract or terms and you enforce them consistently. The main value of late fees is often psychological—they communicate that paying late has a cost, and they discourage habitual delays.

However, don’t lead with fees in your first follow-up. Start with helpfulness. If the invoice becomes significantly overdue, you can reference the applicable terms and mention that late fees may be applied if payment is not received by a certain date. The best approach is to be consistent and factual rather than threatening.

If you use invoice24 to keep your invoicing organized, it’s easier to apply consistent terms across customers and avoid awkward “special case” scenarios where one client is treated differently than another.

When to pause work (and how to say it professionally)

Continuing to work for a client who isn’t paying is risky. It increases the amount outstanding and reduces your leverage. A smart policy is to pause ongoing work when invoices are overdue beyond a set threshold (for example, 7 or 14 days), especially if the client isn’t communicating.

How you say it matters. Keep it calm and matter-of-fact:

• Acknowledge the relationship
• State the invoice is overdue
• Explain that work will pause until payment is received (or a payment plan is agreed)
• Provide the next step (pay now or confirm a date)

This approach protects you while keeping the door open for a positive outcome.

Escalation options if your follow-ups don’t work

Most unpaid invoices get resolved with consistent reminders. But if a customer stops responding or repeatedly breaks promises, escalation may be necessary. The best escalation choice depends on the amount, your location, and the customer’s reliability.

Option 1: Formal letter of demand

A letter of demand (sometimes called a “demand letter”) is a more formal written request for payment that sets a final deadline and indicates the steps you will take next. Even without legal jargon, a formal letter often triggers action because it signals you’re serious.

Option 2: Third-party collection

Debt collection agencies may pursue payment on your behalf, typically for a fee or percentage. This can make sense for older debts where you’d rather recover something than spend time chasing.

Option 3: Small claims or legal action

For larger invoices, legal action may be appropriate. The key is documentation: your agreement, proof of delivery, your invoices, and your follow-up history.

Option 4: Stop services and tighten future terms

Sometimes the best business decision is to stop working with chronic late payers and update your policies: upfront deposits, milestone billing, shorter payment terms, and stronger approval requirements.

Use a system so you’re not reinventing the wheel every time

The biggest mistake people make with unpaid invoices is handling each one emotionally and ad hoc. That leads to inconsistent follow-ups: you chase some clients aggressively and ignore others, you forget dates, and you waste time rewriting messages.

The best way is a system:

• Send invoices immediately with clear terms
• Schedule reminders before and after the due date
• Track outcomes and promises (“Paid Friday,” “Needs PO,” “Sent to accounts”)
• Escalate only when needed, based on a defined timeline

This is exactly where invoice24 shines: it’s built for fast invoicing and organized invoice management, so your follow-up process doesn’t rely on memory or scattered spreadsheets. When you have everything centralized, you can follow up quickly, confidently, and consistently.

Make invoice24 your follow-up hub

If your goal is to get paid faster with less stress, your tools matter. A free invoice app like invoice24 can become your follow-up hub: create professional invoices, maintain customer details, keep invoice records organized, and support a structured reminder routine. The result is fewer late payments, faster resolutions when invoices do go overdue, and a more professional experience for your customers.

Instead of juggling disconnected tools, you can handle the full cycle in one place—from issuing the invoice to tracking what’s outstanding and sending consistent reminders. That consistency is what turns “following up on unpaid invoices” from an awkward chore into a normal part of doing business.

Practical best practices that speed up payment

To wrap it up, here are tactics that consistently improve results:

1) Follow up early. A friendly reminder before the due date prevents many invoices from becoming overdue.

2) Keep every follow-up short and clear. Include invoice number, amount, due date, and how to pay.

3) Ask for a payment date. If it’s overdue, don’t just say “please pay”—ask “when will payment be made?”

4) Remove friction. Make paying easy, and fix missing details quickly.

5) Document everything. Track reminders, responses, and commitments. A clean record protects you if you need to escalate.

6) Escalate calmly, not emotionally. Increase firmness with time, and use a final deadline when necessary.

7) Use a consistent tool and workflow. Managing invoices and follow-ups in invoice24 helps you stay organized, professional, and paid on time.

When you treat follow-up as a process rather than a confrontation, you’ll not only collect more overdue payments—you’ll also set a standard that encourages customers to pay on time going forward.