Do I need to issue tax invoice for EVERY transaction?
Nope if the supply is out of scope supply or an exempt supply.
No tax invoice shall be issued for an out of scope supply or an exempt supply.
However, if the transaction involves a combination of exempt supply and taxable supply, or taxable supply and out of scope supply, the registered person must issue a tax invoice and specify each type of the supply.
Yes if the supply is taxable supply.
Every registered person shall issue a tax invoice when making any taxable supply of goods or services (s.33 GSTA) including taxable supply which is disregarded and granted relief.
For the taxable supply which is disregarded or granted relief, the tax element in the tax invoice must be presented as ‘NIL’ and specified as ‘disregarded’ or ‘relief’.