Automate your invoice chasing in one afternoon (free template)

What you'll have by tonight: a workflow that reads your invoice list from a Google Sheet every morning at nine, works out who's overdue, and sends the right reminder — friendly at 7 days, firmer at 14, final at 30 — then records what it sent so nobody gets nagged twice. You'll never again discover in week five that nobody chased the S$8,400 invoice from week one.

No statistics theatre here: if you run a services business in Singapore, you already know late payment is a cash-flow tax and that chasing feels awkward, so it gets skipped. The fix isn't motivation. It's a machine that is politely incapable of feeling awkward.

What you're building

A three-step reminder ladder driven by one spreadsheet:

Guardrails built in: invoices marked Paid are never emailed, nobody is re-reminded within 6 days, and rows with a missing email or unreadable due date are skipped, not guessed at. Every send is logged back into the sheet.

Pick your engine (three honest options)

Option A — n8n, self-hosted (what our template targets). n8n's standard self-hosted version is free (the Community Edition on GitHub); you pay only for somewhere to run it — the cheapest mainstream VPS is about US$4/month (DigitalOcean's smallest Droplet, as listed 12 Jul 2026). If self-hosting sounds scary, n8n Cloud starts at €20/month billed annually — and on n8n, one workflow run counts as a single execution regardless of steps, which suits a daily batch job like this. Choose this route if you (or your one technical person) can follow a Docker tutorial. It's the cheapest at volume and your data stays on your box.

Option B — Make. No server, visual canvas, and its free tier (1,000 credits/month) will usually cover a daily invoice sweep for a small firm; paid starts at US$9/month. Choose this if self-hosting is a non-starter but you're happy to learn a builder for an afternoon. (Disclosure: that Make link is an affiliate link — if you subscribe we may earn a commission at no extra cost to you; how we're funded. The free tier is genuinely enough for many readers, and we say so anyway.)

Option C — Zapier. Simplest builder, but this workflow needs more than two steps, which puts it on a paid plan ("from $19.99/month" at 11 Jul 2026). Pick it if your team already lives in Zapier and the subscription is already paid for. Full comparison: Make vs Zapier for Singapore SMEs.

The build, step by step

The walkthrough below matches our free n8n template exactly; on Make or Zapier, recreate the same five stages with their equivalent modules.

1. Set up the sheet (10 minutes)

One Google Sheet, one tab named Invoices, these columns in row 1 — exactly:

InvoiceNo | ClientName | Email | AmountSGD | DueDate | Status | LastReminded

Dates as YYYY-MM-DD (2026-06-30). Status is either Paid or anything else (Sent, Unpaid, blank). Leave LastReminded empty; the workflow owns that column. Populate it with your real receivables — that step alone is a useful audit.

2. Import the template (5 minutes)

Download invoice-chaser-n8n.json, then in n8n: Workflows → Import from file. You'll see five working nodes plus sticky notes explaining each one: a 9 am schedule trigger, a Sheets reader, a Code node with the ladder logic, the email sender, and a Sheets updater. The README covers connecting your Google and mail accounts (n8n walks you through OAuth; you're granting your own instance access to your own accounts).

3. Understand the ladder logic (5 minutes — really, read it)

The Code node computes daysOverdue = today − DueDate and picks a ladder step: 7+, 14+, or 30+. It skips a row when Status = Paid, when Email is empty, when the date won't parse, or when LastReminded is less than 6 days ago. Change the thresholds by editing three numbers at the top of the node. Nothing else in the workflow needs touching.

4. Steal these emails (10 minutes to personalise)

Step 1 — day 7, friendly:

Subject: Invoice {{InvoiceNo}} — gentle reminder

Hi {{ClientName}},

Hope things are going well. Just a note that invoice {{InvoiceNo}} for S${{AmountSGD}} was due on {{DueDate}} and hasn't come through yet. Quite possibly it's already in motion — if so, please ignore this.

If it's slipped through the cracks (happens to all of us), the payment details are on the invoice. Give me a shout if you'd like it resent.

Thanks!

Step 2 — day 14, firmer:

Subject: Invoice {{InvoiceNo}} — now 2 weeks overdue

Hi {{ClientName}},

Following up on invoice {{InvoiceNo}} (S${{AmountSGD}}, due {{DueDate}}) — it's now more than two weeks past due and I haven't heard back.

Could you let me know when payment will be made? If there's an issue with the invoice or the work, tell me directly and we'll sort it out.

Regards,

Step 3 — day 30, final notice (still no lawyers):

Subject: Final reminder — invoice {{InvoiceNo}}, 30 days overdue

Hi {{ClientName}},

Invoice {{InvoiceNo}} for S${{AmountSGD}} is now a month past its due date of {{DueDate}}, with two reminders sent. I need payment or a payment date within the next 7 days.

If payment has been made in the last day or two, thank you — please disregard. Otherwise I'll pause further work until this is settled.

Regards,

Keep your edits in the same temperature range: warm → direct → firm. Threats you wouldn't act on train clients to ignore you.

5. Test before you trust (15 minutes)

Add two fake rows pointing at your own email — one 8 days overdue, one 31 — and run the workflow manually. Check: the right templates arrived, LastReminded got today's date, and the Paid row stayed silent. Run it manually again immediately — nothing should send (the 6-day guard). Only then switch the schedule on.

Who shouldn't bother

If you issue three or four invoices a month to clients who mostly pay on time, a monthly calendar reminder and five minutes of your bookkeeping beat maintaining any workflow. Automation earns its keep from repetition; below roughly ten receivables a month, this is a hobby, not a saving. (More on that honesty threshold in the Make vs Zapier verdict.)

FAQ

I use Xero/QuickBooks — do I need this? Check your accounting software's built-in reminders first; both have them, and native beats glued-on. This template earns its place when you want a custom ladder and copy, reminders across systems your accounting tool doesn't see, or a LastReminded audit trail your whole team can read in a sheet.

Is emailing payment reminders okay under the PDPA? Chasing your own invoices is using a client's contact details for the purpose they were collected for — billing the work they engaged you for. That's ordinary business use. What you shouldn't do is quietly add those addresses to a marketing list; that's a different purpose needing its own consent. (The template's sticky note says the same thing where your team will actually see it.)

What about clients who pay by cheque or bank transfer with no reference? The sheet is the source of truth, so reconcile it weekly — mark rows Paid when money lands, whatever the channel. The workflow only ever knows what the sheet knows; a stale sheet sends awkward reminders.

Can it send WhatsApp reminders instead? Not out of the box, deliberately — customer-facing WhatsApp requires Meta's Business Platform setup and template approvals (details here). Email is the right channel for money conversations anyway: it's calm, it's threaded, and it's evidence.

Next step

Download the template and README, block one afternoon this week, and do steps 1–5 in order. When it's been running quietly for a fortnight, put your numbers through the grant-stacking calculator before you buy anything bigger — and if a vendor quotes you a five-figure "automation package" for what you just built free, you know which article to read next.