Hmm, eg. you loan 500k. Maybe you are very rich, got lotsa cash. You you take flexi loan.
In flexi loan, you got 1 housing account + 1 current account.
Housing account = 500k that you borrow, will reduce slowly when you pay.
Current account is the account that you can put in your extra money.
Why? Your interest is calculated on daily basis. This is how they charge interest on you.
Housing account - Current account = interest charged.
So example above, you loaned 500k, you take 300k from your fixed deposit (or any money from anyway that you have extra), put into that current account.
Your interest will be calculated based on below:
500k - 300k = 200k

They will only charge you based on that remaining amount, and calc everyday. So it will be diff everyday

The more you have in your current account, the more interest you save.
But you cant dump in 500k into current account, because if like that bank would not be able to charge you any interest. You will be paying only your principle (housing loan). Thats why there is a prepayment rule. 70% out of 500k means max you can put in current account is 350k so bank can always earn abit from you from that remaining 30% (150K of chargeable interest)
Varies with banks.
Please correct me if im wrong. Do not want to misleading