DEV Community: Ledgerline Tools

Build an invoice reminder workflow in n8n with Google Sheets (idempotent, AU GST wording)

Ledgerline Tools — Fri, 16 Oct 2026 11:13:12 +0000

Flow: Schedule Trigger (daily 9am, workflow timezone set) → Google Sheets "Get rows" → Code node (decide) → Send Email (SMTP) → Google Sheets "Update row" (match on row_number).

The decision logic

Skip rows where status is paid, cancelled or on hold.
daysFromDue = today − due_date. Accept both YYYY-MM-DD and DD/MM/YYYY.
Stages = [−3, 0, 7, 14, 30]. Pick the highest stage whose offset ≤ daysFromDue, so downtime doesn't cause a burst of emails.
Send only if that stage's index is greater than the stored last_stage_sent index (idempotent).
Write back last_stage_sent and last_sent_date.

Gotchas we hit

Send Email v2.1 appends an n8n attribution footer by default. Turn it off under Options.
Importing with n8n import:workflow fails if the JSON has no id.
Test against a local SMTP catcher (e.g. Python aiosmtpd) before touching a real inbox.

AU GST wording

If the business is GST-registered: "Tax invoice … Total includes GST of $X", where X = total ÷ 11 rounded to the cent. Otherwise: "Invoice … No GST has been charged".

Packaged version with guide, sample sheet and 5 templates: https://ledgerlinetools.gumroad.com/l/au-invoice-chaser

Published by Ledgerline Tools, a small Australian automation studio. Questions: ledgerlinetools@proton.me

NZ GST return (GST101A) boxes 5–15 explained, with 2026-27 due dates

Ledgerline Tools — Fri, 16 Oct 2026 11:08:04 +0000

NZ GST is 15%. The GST in a GST-inclusive amount = amount × 3/23 ($115 includes $15).

Box	What goes in it
5	Total sales and income for the period, including GST and zero-rated supplies
6	Zero-rated supplies included in Box 5 (usually exports)
7	Box 5 − Box 6
8	Box 7 × 3 ÷ 23
9	Adjustments (from your calculation sheet)
10	Box 8 + Box 9: total GST collected
11	Total purchases and expenses including GST (excluding imported goods)
12	Box 11 × 3 ÷ 23
13	Credit adjustments
14	Box 12 + Box 13: total GST credit
15	Difference between Box 10 and Box 14. If 10 is bigger you pay; if 14 is bigger you get a refund

(Source: IRD GST guide IR375 and the GST101A return.)

2-monthly due dates (31 March balance date)

GST returns are due on the 28th of the month after the period ends, except periods ending 30 November (due 15 January) and 31 March (due 7 May). Weekend or public holiday: next working day.

Apr–May 2026: 28 Jun 2026 (a Sunday, so Mon 29 Jun)
Jun–Jul: 28 Aug 2026
Aug–Sep: 28 Oct 2026
Oct–Nov: 15 Jan 2027
Dec–Jan: 28 Feb 2027 (a Sunday, so Mon 1 Mar)
Feb–Mar: 7 May 2027

(NZ public holidays haven't been checked against these dates.)

Do you need to register?

Yes, if your turnover was at least $60,000 in the last 12 months or will be in the next 12. (IRD: Registering for GST.)

General information, not tax advice.

Published by Ledgerline Tools, a small Australian automation studio. Questions: ledgerlinetools@proton.me

BAS G1, 1A and 1B explained for sole traders (with a worked example and FY2026-27 due dates)

Ledgerline Tools — Fri, 16 Oct 2026 11:02:50 +0000

If your GST turnover is under $10 million, you're on Simpler BAS and report just three GST labels:

G1 Total sales: all your sales for the quarter, whether taxable, GST-free or input-taxed (including exports). Tick whether the figure includes GST.
1A GST on sales: the GST in your taxable sales (taxable amount ÷ 11).
1B GST on purchases: the GST credits on business purchases. You need a tax invoice for purchases over $82.50, and only the business-use share counts.

(ATO: Instructions for completing your BAS, Step 1: Sales, Step 3: Purchases.)

Worked example (Q1, July–September 2026)

Sale	Amount	Treatment
Electrical repair	$1,320	Taxable
Tiling	$880	Taxable
Goods exported to NZ	$2,000	GST-free export

G1 = $4,200 (GST-inclusive)
1A = $1,320 ÷ 11 + $880 ÷ 11 = $120 + $80 = $200

Purchase	Amount	Business use
Materials	$440	100%
Phone	$99	60%
Laptop	$2,200	100%

1B = $40 + $5.40 + $200 = $245.40
Net: 1A − 1B = −$45.40, so you'd get a refund of about $45.

Report whole dollars, rounded down (G1 $4,200, 1A $200, 1B $245). No cents and no negative signs on the form.

FY2026-27 quarterly due dates (lodge and pay)

Quarter	Due
Q1 Jul–Sep 2026	28 Oct 2026
Q2 Oct–Dec 2026	Tue 2 Mar 2027: 28 Feb is a Sunday and Mon 1 Mar is WA Labour Day, so the ATO moves it to the next business day (aim for 1 Mar to be safe)
Q3 Jan–Mar 2027	28 Apr 2027
Q4 Apr–Jun 2027	28 Jul 2027

Lodging online may give you 2 extra weeks (not for Q2). Tax and BAS agents may have different dates. Your BAS shows your actual due date. (ATO: Due dates for lodging and paying your BAS.)

General information, not tax advice. Ledgerline Tools' GST & BAS Workbook does these calculations from your income and expense records: https://ledgerlinetools.gumroad.com/l/au-gst-bas-workbook

Published by Ledgerline Tools, a small Australian automation studio. Questions: ledgerlinetools@proton.me

Tax invoice vs invoice in Australia: what must be on it (ATO checklist)

Ledgerline Tools — Fri, 16 Oct 2026 10:56:33 +0000

Short answer: only GST-registered businesses issue tax invoices. If you're not registered, you issue an invoice with no GST on it.

When you need a tax invoice

You're registered for GST and make a taxable sale.
If a customer asks for one, you must provide it within 28 days, unless the sale is $82.50 (inc GST) or less.
Your customers need a tax invoice to claim GST credits on purchases over $82.50. (ATO: When you can claim a GST credit.)

The 7 things a tax invoice must show (sales under $1,000)

That it's intended to be a tax invoice
Your identity
Your ABN
The date it was issued
A brief description of what you sold, including quantity (if applicable) and price
The GST amount, or "Total price includes GST" if GST is exactly one-eleventh of the total
The extent to which each item is taxable

$1,000 or more: add the buyer's identity or ABN. (Source: ATO, Tax invoices, updated 18 Sep 2026: https://www.ato.gov.au/businesses-and-organisations/gst-excise-and-indirect-taxes/gst/tax-invoices)

Working out the GST

GST in a GST-inclusive price = price ÷ 11. $1,100 includes $100 GST. Round to the nearest cent.

If you're not GST-registered

Head it "Invoice", include your ABN, and say "No GST has been charged". You must register once your GST turnover reaches $75,000. That's tested on the current month plus the previous 11, or the projected next 12 months. (ATO: Registering for GST.)

Digital invoices are fine

A PDF emailed to the customer is a valid tax invoice if it contains everything above.

Ledgerline Tools makes small admin tools for Australian sole traders. This is general information, not tax advice.
Related: the GST & BAS Workbook works out G1, 1A and 1B from your records: https://ledgerlinetools.gumroad.com/l/au-gst-bas-workbook

Published by Ledgerline Tools, a small Australian automation studio. Questions: ledgerlinetools@proton.me

How to chase an unpaid invoice in Australia: 5 polite email templates (copy-paste)

Ledgerline Tools — Fri, 16 Oct 2026 10:55:36 +0000

Late payment is the most common cash-flow headache for sole traders. The fix is mostly boring: a consistent schedule, polite wording, and a clear invoice. This guide gives you all three.

Step 0: make sure the invoice is right

If you're registered for GST and the customer asks for a tax invoice, you must provide one within 28 days (unless the sale is $82.50 inc GST or less). A tax invoice needs: the words "Tax invoice", your identity and ABN, the issue date, what you sold (quantity and price), the GST amount (or "Total price includes GST" when GST is exactly 1/11 of the total), and how much of each item is taxable. For sales of $1,000 or more, it also needs the buyer's identity or ABN. (Source: ATO, Tax invoices, last updated 18 Sep 2026.) Not registered for GST? Call it an "Invoice" and say no GST has been charged.

The 5-step schedule

When	Tone	Goal
3 days before due	Friendly heads-up	Catch the "forgot" cases
Due date	Gentle reminder	Make it easy to pay today
+7 days	Polite overdue	Ask if there's a problem
+14 days	Firm second notice	Set a 7-day deadline
+30 days	Final notice	Mention pausing work and next steps

The templates

1. Three days before: "Hi {name}, just a quick heads-up that invoice {number} for {amount} is due on {date}. If it's already scheduled, thank you, and please ignore this email. Payment details: {BSB/account or pay link}."

2. Due date: "Hi {name}, a reminder that invoice {number} is due today. If you've already paid, thank you, and please disregard this."

3. +7 days: "Hi {name}, our records show invoice {number} is now 7 days overdue. It may simply have slipped through. Could you arrange payment, or let me know if there's an issue with the invoice?"

4. +14 days: "Hi {name}, invoice {number} for {amount} is now 14 days overdue and I haven't heard back. Please arrange payment within the next 7 days, or reply to let me know when it will be paid. If there's a problem with the work, I'm happy to discuss it."

5. +30 days: "Hi {name}, despite previous reminders, invoice {number} remains unpaid 30 days after its due date. Please pay the full amount within 7 days, or contact me today to agree a payment plan. If I don't hear from you, I may need to pause further work and consider next steps to recover the debt."

Tips that actually help

Put the payment details in every email. Every extra click delays payment.
Send from your normal email, so replies come back to you.
Keep a simple sheet: invoice, due date, last reminder sent. Stop the moment it's paid.
Don't threaten anything you won't do. This guide isn't legal advice; for debt recovery, get advice.

Want this on autopilot?

If you use n8n, the AU Invoice Chaser sends exactly this schedule from a Google Sheet, with ATO tax-invoice wording, and logs each reminder so nothing goes twice: https://ledgerlinetools.gumroad.com/l/au-invoice-chaser

Free download: these 5 templates as a PDF: https://ledgerlinetools.gumroad.com/l/payment-reminder-templates

Published by Ledgerline Tools, a small Australian automation studio. Questions: ledgerlinetools@proton.me