By Marc Alexander

Australian online stores show prices with GST included, because the law requires it. GA4 expects revenue without tax. When nobody bridges that gap, GA4 overstates revenue by the GST in every order.

Two rules that pull in different directions.

Under the Australian Consumer Law, prices shown to consumers must be a single total that includes GST. So the price on the product page, in the basket and at checkout all include it.

Google's reference for the GA4 purchase event says value should be the sum of each item's price times its quantity, and shouldn't include tax or shipping. Those have their own parameters, tax and shipping.

Most stores pass the prices they display straight to GA4, so GST ends up inside revenue.

Why it matters.

  • Revenue is overstated by the GST in each order: one eleventh, or about 9%, of the GST-inclusive price on taxable products.
  • Return on ad spend is overstated by the same amount, so campaigns look more profitable than they are.
  • It won't match finance. Accounts report sales excluding GST, so GA4 and the finance team disagree before anyone looks for a tracking problem.
  • Mixed baskets distort. Some products, such as many basic foods, are GST-free, so a flat assumption doesn't work either.

Doing it properly.

  1. Send item prices excluding GST. Each item's price in the items array should be the price before GST, so item revenue and purchase revenue agree.
  2. Set value to the items' total excluding GST.
  3. Send GST in tax and delivery in shipping, so nothing is lost.
  4. Use currency: "AUD" on every ecommerce event.
  5. Work it out from the order, not a formula. Your platform knows the GST on each line. Dividing everything by 1.1 gets GST-free products wrong.
  6. Send Google Ads the same figure, so GA4 and Ads agree and bidding learns from real revenue.

Some businesses decide to report revenue including GST anyway. That can be fine, as long as it's a decision, written down, and applied everywhere: GA4, Google Ads, Meta and reports.

What to check.

  1. Place a test order and look at the purchase event in GA4's DebugView.
  2. Check whether value includes GST, and whether tax is sent.
  3. Add up the item prices and compare with value.
  4. Repeat with a GST-free product in the basket.
  5. Compare a week of GA4 revenue with sales excluding GST from your platform.

Payment options cause a second common gap, covered in Afterpay, Zip and PayPal referrals in GA4. The guide to GA4 revenue not matching Shopify or Stripe has the reconciliation steps. Marc Alexander sets up ecommerce tracking for Australian stores, and the GA4 mini audit checks your revenue against your platform.