Open-source playbook · 17 of 20 · For ops, finance and HR
Cash sits in overdue invoices because chasing them is awkward and manual.
The systemSends the right reminder at the right time, logs every reply and flags disputes to finance.
// The problem
Reminders are awkward to write and easy to put off. So they go out late, in a different tone each time, and the replies sit in one person’s inbox. The older an invoice gets, the harder it is to collect.
$581,300 owed by customers$169,000 of it overdue
Not yet due
$412,300
64 invoices
Who chases itNobody needs to
1–30 days
$96,800
22 invoices
Who chases itSometimes, if someone remembers
31–60 days
$41,200
9 invoices
Who chases itWhoever has a free afternoon
61–90 days
$18,600
4 invoices
Who chases itThe CFO, personally
90+ days
$12,400
3 invoices
Who chases itNobody. Now it’s awkward
Sample receivables, fictional company.
// How it works
Every morning the system checks which invoices are still unpaid and sends the next step from wording finance approved. At 30 days it stops writing to the customer and hands over to a person.
−33 days before due
Invoice INV-2291 is due on 15 October
“A quick heads-up that INV-2291 for $8,450.00 is due on Wednesday. The invoice and payment details are attached.”
Sent automatically
0On the due date
INV-2291 is due today
“Just a reminder that INV-2291 is due today. If it’s already on its way, thank you, and please ignore this.”
Sent automatically
+77 days overdue
INV-2291 is now 7 days overdue
“We haven’t received payment yet. Could you let us know when to expect it? If something’s wrong with the invoice, just reply.”
Sent automatically
+1414 days overdue
INV-2291: second reminder
“INV-2291 is now two weeks past due. Our terms are 30 days from the invoice date. Please arrange payment this week, or reply with a date.”
Sent automatically
+3030 days overdue
INV-2291: can we talk?
“I’d like to sort this out with you directly. Could you call me on 555-0142, or reply with a time that suits you?”
Drafted. Finance reviews and sends
A reply at any step leaves the ladder. Disputes and promises to pay go to finance, never to the next reminder.
Paid? It checks the accounting tool before every send, so a paid invoice is never chased.
// The off-ramp
Two sample replies from a fictional customer. The system reads each one, stops the reminders and tells finance what happened and what it suggests. It doesn’t answer the customer itself.
Reply to the +7 reminder
Maria Chen, Orchard Lane Grocers
“We were charged for 40 cases but only 36 arrived. We’ll pay once the invoice is corrected.”
The system
Sounds like a dispute
All reminders for INV-2291 stopped
Finance · #finance-flags
Orchard Lane disputes INV-2291: 4 cases short. Thread and delivery note attached. Suggested next step: check the delivery record, then decide on a credit note.
Nothing is sent to the customer until Dev decides.
Reply to the +14 reminder
Maria Chen, Orchard Lane Grocers
“Our payment run is on the 31st, you’ll have it then.”
The system
Promise to pay: 31 Oct
Reminders paused until 3 Nov
Finance · #finance-flags
Orchard Lane promises to pay INV-2291 on 31 October. Logged on the invoice in Xero.
If it isn’t paid by 3 November, it comes back to Dev, not to the next reminder.
// Who signs off
Nothing goes out until finance has approved the wording, the schedule and who’s left out. Anything beyond a reminder, like a late fee, an account hold or a phone call, stays a person’s decision.
What it never does
Collections rulesApproved by Dev Patel, Finance
Sample settings, fictional company. Change a rule and the next morning’s run follows it.
// For your tech lead
Your accounting tool already knows which invoices are open and when they’re due. The build is a daily check, five approved messages and one rule: every reply goes to a person.
| Job | Use | Or |
|---|---|---|
| Open invoices and due dates | QuickBooks Online or Xero | FreshBooks, NetSuite |
| Running the daily check | n8n on a schedule | Make, Zapier |
| Sending reminders | Gmail or Outlook, from a finance mailbox | QuickBooks or Xero’s built-in reminders |
| Reading replies | Claude (API), sorting each reply | ChatGPT, Gemini |
| Where finance sees flags | A Slack channel | Teams, a shared finance inbox |
Start simple1 day
Turn on the reminders built into QuickBooks or Xero with wording finance approves, and send replies to a shared finance inbox.
Production2–3 days
n8n checks open invoices every morning, sends the next step from your templates, reads every reply, and pauses and flags disputes and promises to finance.
Custom1–2 weeks
Adds rules per customer, a weekly aging report that explains what moved, and call notes for finance at the 30-day step.
A finance or ops person can build it in two to three days with n8n. Finance owns the wording, the schedule and every flag, and someone checks the flag channel each morning.
Needs
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