How We Automated Invoice Chasing for a 50-Client Agency

The Problem

James runs a digital marketing agency with around 50 active clients at any given time. Invoicing was fine — he had a system. Chasing was not. Every Friday afternoon he would open a spreadsheet, filter for unpaid invoices, and write individual follow-up emails to each late client. Sometimes five. Sometimes fifteen. Always manual, always time-consuming, always falling behind other work.

"Friday was basically ruined," he told us. "Three, sometimes four hours just writing the same emails. 'Hi [Name], just following up on invoice #123...' I'd been doing it for three years."

Beyond the time loss, there were real revenue consequences. Invoices that slipped past the first Friday chase sometimes didn't get followed up again for two or three weeks — by which point clients had moved on mentally and the money felt harder to collect. His average debtor days had crept up to 47.

What He Actually Needed

After a quick call, the brief was straightforward. James needed three things:

• Automatic detection of overdue invoices from his existing invoice system
• Personalised chase emails sent via Gmail — not a generic template, something that felt like it came from him
• A Slack alert so he could see what had been sent without logging in anywhere

He wasn't looking for a new invoicing tool or an accounts receivable platform with a £200/month price tag. He wanted his existing setup to just… do the work it wasn't doing. n8n was the right tool for this: it connects to any API, runs on a schedule, and doesn't require building anything from scratch.

What We Built

Here's the full workflow we shipped:

The workflow fires twice a week — Monday morning and Thursday afternoon. It pulls the full list of open invoices from his invoice system via API, filters for anything more than 7 days past due, and segments by how long overdue: 7–14 days gets a polite nudge, 15–30 days gets a firmer reminder, and 30+ days triggers a different template that flags the invoice as requiring urgent attention.

The email generator node personalises each message using the client name, invoice number, amount, and due date pulled live from the API. The tone matches what James would have written himself — we built the templates from a dozen of his actual chase emails, so the voice is consistent. Clients don't know it's automated.

After each send batch, a Slack message drops into the #invoices channel with a quick summary: how many chases went out, total value outstanding, and any invoice that's been chased more than three times (flagged for a personal call). James can see the whole picture in 10 seconds every Monday morning instead of spending Friday afternoon buried in email.

The build took about two and a half days. One day setting up the API connections and n8n flow, one day on email template logic and personalisation, half a day testing edge cases with real invoice data.

The Result

The 15% figure surprised James. "I assumed most of those invoices would come in eventually," he said. "But some of them were genuinely just… waiting for someone to ask. Clients aren't sitting there thinking about our invoice — they're thinking about their own stuff. A polite email at the right time is all it takes."

The other thing worth noting: the consistency matters. Manual chasing is inconsistent by nature — some Fridays he had time, some he didn't. The automation runs at exactly the same time, every week, regardless of what else is happening. That regularity on its own seems to have changed how clients perceive the invoicing process.

What This Actually Cost

This was a focused, single-workflow build — scoped under our Starter plan. James paid a fixed price, received the full n8n workflow exported and documented, and has been running it independently since day one. No ongoing fees to us, no retainer, no black box.

If your business has a similar problem — revenue sitting uncollected because nobody has time to chase it — get in touch. The call is free and we'll tell you honestly whether automation is the right move.