Any tool to quickly raise an invoice to a business? I don't have an entity / GST etc set up.

@acceptable-flag-71699 http://invoice.zoho.com/ If you are going to raise another invoice ever - helpful. Else, takes a bit of setting up (~ 5 mins of work) Recently, I used a simple word document. 🤷

This seems easier: https://www.zoho.com/invoice/free-invoice-generator.html But is it mandatory for me to have a GSTIN ?

Nope. Of course not

How do you receive payments? Cheques? Netbanking?

Yes. Netbanking / wire transfer for software work. RazorPay / Instamojo for PrintsToday.

I use invoice simple in App Store (with orange and white tick mark)