Tax Invoice:

When a company sells a product to distributor or any person
in the supply chain but not the end user then Tax invoice is
generated because it is going to be resold. To issue a Tax
Invoice the person who purchases a product must have TIN
(Tax Identification Number).

Retail Invoice:

When an end user of the product is purchasing then consumer
receives the retail invoice.

Main and straight difference between Tax Invoice and Retail
Invoice is Tax invoice is entitled to Input Tax Credit in
(VAT) whereas Retail Invoice is not because product is not
going to be resold by consumer.