Tax invoice vs bill of supply

Both are sale documents, but they are for different situations.

Tax invoice

Issued by a regular GST-registered business for a taxable supply. It shows GST separately (CGST and SGST, or IGST).

Bill of supply

Issued when no GST is charged: by composition-scheme dealers, or for exempt goods, or by businesses below the registration threshold. It does not show GST.

If you are registered and charging GST, you issue a tax invoice. Make one free here.