It is possible that GST is not configured properly in your Bigcommerce store.

If you sell products that include a GST component, your settings should reflect this.

An example is provided below, please check out the Bigcommerce documentation for more info.

Please check these:

Upper right corner, Setup & Tools -> Tax -> Prices Entered With Tax option (see screen capture)


Check that the correct GST tax zone and rate is defined:

Products that are Tax Free

If you have one or more products that are tax free, the recommended settings are like this:

  1. Enter prices exclusive of tax.
  2. Make sure there's a "Non-Taxable Products" rate and the value is zero (see image above)
  3. Make sure you select Tax Class: Non-Taxable Products in the product details screen:

Basically, you need to follow the advice in the help popup window next to the Tax Class field:

"If this product should not be taxable, you should create a 'Non-Taxable Items' tax class, leave it at 0% for your tax rates and then select it for this product."