Prepaying a loan — paying more than your scheduled EMI — is one of the few genuinely "free lunch" financial moves available to borrowers, because the savings are guaranteed and risk-free, unlike investment returns which fluctuate. Every extra dollar you pay above your scheduled EMI goes 100% toward reducing your principal, which permanently lowers all future interest calculated on that smaller remaining balance.

Because interest each month is calculated on your outstanding balance, and that balance is highest at the very start of a loan, prepaying early in the loan term saves dramatically more interest than prepaying the same dollar amount later. A $5,000 prepayment in month 3 removes that $5,000 from accruing interest for nearly the entire remaining loan term — potentially 20+ years on a mortgage. The same $5,000 prepayment in year 25 of a 30-year mortgage only removes interest accrual for the remaining 5 years, a far smaller cumulative benefit.

Consider a $300,000 mortgage at 6.5% over 30 years (360 months). The standard EMI is approximately $1,896/month, and total interest paid over the full term (with no prepayment) is roughly $382,560.

Notice the diminishing but still substantial returns: doubling your extra payment from $100 to $300 doesn't simply double your interest savings — it more than doubles it in this case, because larger early prepayments compound their balance-reducing effect over more remaining months.

A single lump sum prepayment delivers its entire balance-reducing effect at once, on the date it's applied — meaning a lump sum applied very early in the loan can be even more powerful than the same total amount spread out as smaller monthly extra payments over a longer period, simply because the money is removed from interest-accrual sooner. That said, recurring extra payments have a practical advantage: they don't require having a large sum of cash available at once, making them realistic for ordinary monthly budgets.

When you prepay, most lenders give you a choice (or default to a specific policy) on how the benefit is applied:

This is the single most important strategic question around prepayment. Compare your loan's interest rate to your realistic, after-tax expected investment return. If your mortgage carries a 7% rate and you could realistically expect, say, 8-9% average annual returns investing in a diversified portfolio over the same horizon, investing may build more wealth — though prepaying carries zero risk and a guaranteed return, while investing carries market risk. Many financial planners suggest a middle path: prepay aggressively on any debt above 7-8% interest (where the guaranteed "return" from prepaying is hard to beat risk-free), while investing extra cash if your debt rate is meaningfully below typical long-term market returns.