TinyBAS — Simpler BAS worksheet for Australian sole traders

A running Simpler BAS ledger for Australian sole traders. Log invoices and expenses through the quarter — or import a CSV — and copy G1, 1A and 1B into the ATO portal. Offline HTML, no subscription, no Xero. Worksheet only: it does not lodge and it is not tax advice.

WHAT TINYBAS IS

Most "BAS calculators" are one-shot: you already have the totals, you type them in, you get GST. TinyBAS is what you use instead of a messy spreadsheet for the whole quarter. Add (or CSV-import) each sale and purchase as it happens. It keeps a ledger in your browser and, for the quarter you are lodging, shows the only three ATO labels Simpler BAS actually wants:

G1 — Total sales (GST-inclusive where GST applies)

1A GST on sales

1B — GST on purchases

Net GST = 1A − 1B (to pay, or a refund)

Then you copy those figures into the ATO Business portal yourself. Standard quarterly due dates sit on the screen: 28 October, 28 February, 28 April, 28 July.

WHO IT IS FOR

GST-registered Australian sole traders and small ABN holders on Simpler BAS (GST turnover under $10 million) who issue a handful of invoices a quarter, are tired of paying for cloud bookkeeping just to read three boxes, can tell a taxable invoice from a GST-free one, and want a file they can double-click with no account and no cloud.

WHAT'S INCLUDED

tinybas.html — the whole product. Double-click it. Works from file://. No install, no CDN, no internet.

README.txt — how to use it, what G1 / 1A / 1B mean, tax treatments, disclaimer.

sample-transactions.csv — a few sales and expenses so you can test import before you touch live figures.

All data stays in your browser (localStorage). JSON backup / restore is built in.

WHAT YOU CAN DO

Business name, ABN, AU financial year (starts 1 July), quarter selector with due date

Sales and purchases ledgers with Simpler BAS tax treatments (GST included, GST on top, GST-free, out of scope, capital purchases)

Running quarter totals plus a FY-to-date strip

Add / edit / delete, search, CSV import and export, JSON backup

One-click copy of G1, 1A, 1B, or a three-line paste block

Print / Save as PDF (clean worksheet: quarter, totals, line items)

Optional "show working" per line (GST-ex / GST / GST-inc) — not required to lodge

WHAT IT IS NOT — PLEASE READ

TinyBAS is NOT a lodgement tool — it does not talk to the ATO.

It is NOT tax advice and NOT an ATO product.

It is NOT Xero, MYOB or QuickBooks, and not a substitute for a registered tax agent.

It does NOT handle PAYG, FBT, fuel tax credits, or full GST reporting (G2, G3, G10, G11).

It does NOT decide whether a supply is taxable — you do.

It will NOT stop you lodging on the wrong basis (cash vs accruals) — enter dates that match how you account.

DISCLAIMER: TinyBAS is a worksheet only. It is not tax advice, it is not an ATO product, and it is not affiliated with or endorsed by the Australian Taxation Office. Nothing is lodged for you. Always check your figures before you lodge.

DELIVERY AND LICENCE

Instant download: tinybas-v1.zip (tinybas.html, README.txt, sample-transactions.csv). A$19 one-time, yours to keep, no subscription. Version 1.0 — 27 August 2026. No refunds on digital files once downloaded, except where the file will not open contact me and I will replace it.