The Indian laws for an online business plan are:
Company or LLP Registration
GST Registration.
FDI
IT Act (2000)
Payment and Settlement System Act
Consumer Protection Act (2009)
You need to have a Bank Account in the name of your business from where all your transaction takes place.
It is important to agree with the Payment gateways.
Some legal agreements both with the government and the IT Companies for fair conduct of business online.