BAS Calculator Australia 2025-26

Calculate your quarterly BAS in Australia including GST, PAYG withholding, and PAYG instalments. Enter your BAS field amounts to estimate your Business Activity Statement before you lodge and see whether you owe the ATO or are due a refund.

Based on current ATO GST rate of 10%. Enter GST-inclusive amounts for all sales and purchase fields.

Also useful: GST Calculator for line-item GST checks, PAYG Calculator for payroll withholding, and ATO Interest Calculator if you're dealing with overdue BAS amounts.

What is a Business Activity Statement (BAS)?

A Business Activity Statement is a form submitted to the Australian Taxation Office (ATO) by GST-registered businesses. It reports your GST collected on sales, GST credits claimed on purchases, PAYG withholding from employee wages, and PAYG instalments for your own income tax.

If you are registered for GST, you must lodge a BAS — even if you have nothing to report for the period. Most small businesses lodge quarterly, while larger businesses (with turnover above $20 million) lodge monthly.

What does a BAS calculator help with?

Most BAS searches are really about one of three questions: how much GST to pay, how much PAYG to report, and whether the final BAS produces a payment or refund. This calculator is built for that exact workflow, so you can estimate the full statement before you lodge.

How GST is calculated on a BAS

The BAS uses a simple method to calculate your net GST position. All amounts are entered as GST-inclusive totals, and the GST component is extracted by dividing by 11.

If your net GST is negative (you paid more GST on purchases than you collected on sales), the ATO refunds the difference.

BAS fields explained

G1 — Total sales

Report your total sales for the period including GST. This includes all income from goods sold, services provided, and any other business revenue. Include both cash and credit sales.

G2 — Export sales and other GST-free sales

Report any sales that are GST-free. This includes exports, sales of basic food items, medical services, educational courses, and other items listed as GST-free under the GST Act. These are subtracted from G1 before calculating GST.

G10 — Capital purchases

Report purchases of capital assets including GST. Capital purchases are items you buy for long-term business use, such as equipment, vehicles, machinery, or property improvements exceeding $1,000.

G11 — Non-capital purchases

Report all other business purchases including GST. This covers day-to-day operating expenses such as stock, office supplies, rent, utilities, professional services, and contractor payments.

W1 — PAYG withholding

Report the total amount of tax you withheld from payments to employees, directors, and contractors who did not quote a TFN. This amount is remitted to the ATO as part of your BAS.

T1 — PAYG instalment

Report your PAYG instalment amount. This is a prepayment towards your own income tax (or your company's income tax) based on business or investment income. The ATO provides either an instalment amount or a rate to calculate it.

BAS lodging deadlines

BAS due dates depend on your reporting period:

If a due date falls on a weekend or public holiday, the deadline moves to the next business day. Tax agents may have different due dates.

Worked example

Sarah runs a small retail business. For the October–December quarter, her figures are:

• G1 Total sales: $55,000 (including GST)
• G2 GST-free sales: $5,000 (basic food items)
• G10 Capital purchases: $11,000 (new point-of-sale system)
• G11 Non-capital purchases: $22,000 (stock and operating costs)
• W1 PAYG withholding: $4,500 (from two part-time employees)
• T1 PAYG instalment: $1,200 (ATO-advised amount)

Sarah owes the ATO $7,245.45 for this quarter. She must lodge and pay by 28 February (the December quarter has a special extended deadline).