Protect your consumer rights, ask for invoice.
When you pay for a service or goods, not to resale them, you are a consumer.
Legal definition provided in the Consumer Protection Act, 2019
People want to save money by purchasing without invoice. This is either the goods are counterfeit or stolen or people don't want to pay GST, where it is applicable.
There are more benefits to purchase with invoice than purchasing without invoice.
1. Consumer rights can be invoked by using it as evidence.
2. It protects the purchaser from criminal liability if it is found to be stolen goods.
3. It serves as documents to provide to the authority while making complaints when goods are robbed or stolen.
One of my friend made an animation relating to consumer litigation. I hope you like it-