First we'l assume this is a legit income and can prove the source of income, so if we deposit this 100m in a bank, definitely we have 2 pay income tax.
Q1:- how much is the rate of income tax?
different tax rates applies to different income levels/different sources. Only on profit. If a land/property sale there may be capital gain tax
Q2:- what r the document we hav 2 submit?
we have to file income tax return
Then we'l assum this is a legit income and we can not prove the soure of income. As a example, we'l think someone got some money from their grand parents by selling a land property. Bt when he depositting the money he/she cant prove the SOI
Q3:- how can we secure the money?
if you can't prove the source it won't be legitimate.
Q4:- how much can we deposit in a bank without getting any trouble?
not sure may be around 10 lacks
either you have to buy a lottery winning -
or
you can start a Gem mine in rathnapura &buy some gems & sell even then you may be charged for tax but you can use that method to Launder your black money
or
You can use some other cash collecting business to bank your money. Most of the businessmen do is get a big loan & start business. Then start to deposit money in small bulks.
or
Buy golds in informally and keep in safe lockers.
or
podi Tourist hotels keepayak aragena danna. samanya ekaknam gannath beri wei. Loan walata ganna oni passe settle karanna.