All the high denomination notes (~80% of circulating currency) were demonetized in India on 8th November 2016. So all the money in the safe had to be taken to the bank to be exchanged.

And then taking out more than a limit of cash is a very lengthy process now.

So yes, it's not illegal to store cash but it's very difficult. And doing cash transactions above a certain limit are illegal.

Why? Because many business people in India don't pay taxes.