The Client
Name withheld at client request. Sector: plumbing and heating. Location: Hertfordshire (specific town withheld for privacy).
A 6-engineer plumbing and heating business that had been operating in Hertfordshire for 11 years. Turning over approximately £820K/year. Owner-operated with a part-time office manager handling all admin.
The Problem
When I first spoke to the owner, she wasn't looking for an automation consultant. She was looking for a part-time bookkeeper.
Her office manager was spending 4 hours every week chasing unpaid invoices. Manually pulling up Xero, finding overdue accounts, drafting and sending reminder emails one at a time, logging the contact in a spreadsheet, and then doing it again the following week for invoices still unpaid.
The numbers were painful:
- Average payment time: 28 days (against 14-day terms)
- Outstanding debtors at any point: £28,000–£45,000
- Write-offs per year from uncollected invoices: approximately £6,200
The manual process meant follow-up was inconsistent. Busy weeks, the chasing didn't happen. Quiet weeks, it did. There was no logic to it — just whoever had capacity.
The Solution
We didn't need a bookkeeper. We needed a system that never had a busy week.
Over two sessions, I mapped the existing manual process and built a three-stage automated invoice reminder workflow using Zapier and their existing Xero subscription.
Stage 1: 3-Day Reminder (Friendly Nudge)
Trigger: Invoice reaches 3 days past due date in Xero Action: Gmail sends a personalised reminder from the owner's actual email address
The email is warm, assumes good faith ("I know things get busy"), and includes a direct payment link pulled from Xero automatically.
Stage 2: 14-Day Escalation (Firm Reminder)
Trigger: Invoice reaches 14 days past due Condition: Only trigger if invoice is still unpaid in Xero (Zapier checks status before sending) Action: Second email, slightly more direct. References the previous reminder. Includes the business's payment terms and a phone number for billing queries.
Stage 3: 21-Day Escalation (Final Notice)
Trigger: 21 days past due Condition: Invoice still unpaid Action: Third email, formal tone. References potential late payment charges as per the Late Payment of Commercial Debts Act (relevant for B2B clients). Flags that the account will be reviewed if payment is not received within 5 working days.
Implementation Details
Tools used:
- Zapier Professional (£47/month)
- Xero (already paying £28/month)
- Gmail (already using)
- Total additional cost: £47/month
Build time: 6 hours total across two sessions
Testing period: 2 weeks of parallel running (manual + automated) to validate accuracy
One issue we solved: The client had some clients who consistently paid on day 25–30 — technically late, but reliably late and never a problem. We created a Zapier filter that excluded these accounts by tag in Xero, preventing them from receiving reminder emails for accounts that always paid.
Results (6 Months Post-Implementation)
Measured against the 6 months prior to implementation:
| Metric | Before | After | Change |
|---|---|---|---|
| Average payment time | 28 days | 11 days | -61% |
| Office manager time on chasing | 4 hrs/week | 12 min/week | -97% |
| Outstanding debtors (average) | £36,500 | £14,200 | -61% |
| Annual write-offs | £6,200 | £1,800 | -71% |
| Zapier cost | £0/month | £47/month | +£47 |
Net benefit: Approximately £4,400 in recovered write-offs + £19,400 reduction in outstanding debtors + 16 hours/month of office manager time redirected to higher-value work.
Payback period for implementation: Less than 2 weeks.
What the Owner Said
"I genuinely didn't believe it would work this well. The emails go out, clients pay, and I don't have to think about it. My office manager now has time to do things that actually move the business forward."
What Made This Work
Three things made this implementation successful:
-
Sending from a real email address. Reminders from
noreply@addresses get ignored. These come from the owner's inbox and look like a personal message. -
The Xero status check. The "has this already been paid?" check before Stage 2 and Stage 3 emails prevented the embarrassing situation of chasing clients who'd already paid.
-
The exclusions list. Understanding that not every late payer is a problem payer — and building that nuance into the system — meant the client was comfortable switching off the manual process entirely.
Is This Right for Your Business?
This automation works for any B2B service business that:
- Issues invoices through accounting software (Xero, QuickBooks, FreeAgent, Sage)
- Uses Gmail or Outlook
- Has more than 10 outstanding invoices at any given time
If you fit that description, book a free audit and I'll tell you exactly what your implementation would look like.