We have two types of clients: those who buy only the supplies and those who buy both supplies and installation. For clients who buy supplies and installation, it's simple: we add the item and include GST.
However, for clients who buy only the supplies, we must add the amount for each item without GST. Then, the GST is added to the total amount only.
How can I create invoice without GST for each item but automatically adding GST to the total?