I just created a simple sale promotion on some products with a 10% price reduction and it works as it should (also with absolute amount): Strikethrough prices on list and detail view
There must be some problem with your (promotion) setup. What version of HC are you using?

We are using the Price Text field to display the price on the front-end as the list price is listed minus GST in the backend. Not sure if because is using the Price text field as to why it doesn't display the discount?

The price text field can be used to display informations like "ask for a quote". The data type is a string and will (an can) therefore not be altered when discounts are applicable.

If you delete the price text, the amount should be correctly displayed in list and detail view.

Our issue is that we want to apply 10% GST to prices, if we put the prices as cost price minus 10% the prices are shown as all ext GST, but we want to display all prices as inc GST.

If I make all the prices inc GST and set apply VAT rules to off it seems to be ok, but it then adds the GST/VAT to the checkout.

Example:
VAT rules apply Off
Tax set to 10%
Product A = $10 inc GST, price in backend is $10.00 displays as $10 on the site and in the cart, but at checkout, it is making the total cost $11 as it is adding the GST on top of the price.

VAT rules apply On
Tax set to 10%
Product A = $9.09 ex GST, price in backend is $9.09 displays as $9.09 on the site and in the cart, but at checkout, it is making the total cost $10 as it is adding the GST on top of the price. This process seems correct but the display price throughout is not.

Is there a setting or such to display prices inc or ex tax on the listing and detail templates?

This is surely an issue for others, I know woo-commerce makes this process really easy.

Hi Damian

I'm not sure if I understand your problem correctly, but if you want a specific product not to apply GST why don't you create a 0% GST / VAT and apply that to the product?

Like this you have full control over the price and there will be no GST applied on checkout.