I was having the same problem but was unable to find the cause or solution here or in the wiki.

What I found after beating my head on the keyboard for a few hours, was that you may also need to check your settings in:

Sales ->> Sales Types

If the box marked " Tax included: " is checked, FrontAccounting seems to assume that the tax is already included in the item price. Therefore, tax will not show on the sales order or invoice.

It was hinted at by alanmc in one of his replies above but I completely missed it.

Rgds.

You're absolutely correct. Under Sales > Branch, my customer, who is an individual, had 'Tax Exempt' as his Tax Group.
I changed it to Taxable. Now, when a taxable Item is added to a Sales Order, the 'Sales Tax (5.3%)' row appears.

Thanks a million!

The selected customer branch must also be GST.
Then you attempt to test by creating a sales quotation
Add the item to the quotation
Here you would see that changing the price list from Retail to Wholesale shows different taxes on the invoice, included and excluded.

It works for me on all my many setups, unless there is a bug in some of the versions that I do not know about.
Maybe you would share a zip of your FA files, and exported .sql database, might help to understand.

I am using v2.4rc

Rgds.

I have;

           tax_types > GST, 5.3%, 2150 Sales Tax
           tax_group > GST, tax applied to shipping - NO, taxes included in this group - GST (5.3%) checked
   item_tax_types > Retail, is fully tax exempt - NO, tax type which is exempt - NONE checked
                 items > Retail
          sales_type > Retail, calc factor - 1.000%, tax included - unchecked

I can see that the price header in the Sales Order form changes from 'Price Before Tax' to 'Price Including Tax' when I change the drop-down 'Price List' from Retail to Wholesale but there never is any sales tax indicated near the sub-total and is not included in the 'Amount Total'

What am I missing?

See if my steps below might help:

Define your taxes first>>> Tab SETUP--> TAX_TYPES
Each tax_type with one ledger account

Define your tax groups>>> SETUP --> TAX_GROUPS
In my case I have Tax and Tax_Exempt.
Make sure of the tax_type that will be included in each tax_group where it says "Select the taxes that are included in this group".

Define your Item tax types>>> SETUP --> ITEM_TAX_TYPES
In My case I have Regular(15%), Services(6.25%) and Exempt.
Make sure each Item_tax_type is related to its corresponding Tax_Type.

Go to your item, tab ITEMS_AND_INVENTORIES --> ITEMS
Select your item and make sure you have included the correct Item_tax_type for the item.

Then go to tab SALES and down in Maintenance, select SALES_TYPES
Make sure you tick tax_included on the Sale_Type you want tax included, and untick it if you want it excluded.

You would see that when you attempt to create a quotation or invoice, changing from Retail to Wholesale (or however you have named your sales_types) the taxes would be included or excluded immediately on the invoice.

You may give a look to the SETUP Wiki to read extensively on the taxes at the SETUP tab.

I can provide additional details but I'm not sure where to start.

The .sql file is to directly execute in a mysql client like SQLyog, phpMyAdmin, etc if you wanted to set it right without entering in the FA's web UI.

If you followed the screenshots, then you can ignore the .txt and .sql files. They are there for studying the issue and alternative means of fixing for the "gifted and lazy" sysadmins....

References:
https://frontaccounting.com/fawiki/index.php?n=Help.TaxTypes
https://frontaccounting.com/fawiki/index.php?n=Help.TaxGroups
https://frontaccounting.com/fawiki/index.php?n=Help.ItemTaxTypes

After creating the new tax group I notice that the taxes in the first tax group do not appear at all on invoices.  When I switch to a customer defined with the new group, tax3 and tax4 show up as expected.  I can't get invoices to show tax1 and tax2 which were originally okay.

Please help explain/troubleshoot.  Thanks.