TotalTaxV2 calculations return 0 unless order has been placed!

I cannot seem to return the correct TotalTaxV2 amount via the storefront api.

Api Version: 2022-04

Tax settings:

Include or exclude tax based on your customer’s country - On

All prices include tax - Off

Shipping location set and verified.

Tax Region correctly setup for South Africa - 15%.

Each product has charged Tax checked.

Once an order has been placed and i return to the site , using the same shopify_CheckoutUrl - the tax is calculated.
So the checkout object is only correctly populated after an order has been placed.

Please help,
Kind Regards,
Jason