Home Loan Masterclass · Part 11 · Home loans · 10 min read · September 2026

Overdraft home loan: your parked surplus is not prepaying the loan

It is sold as the clever version of a home loan. Park your spare cash against the loan, pay interest only on the difference, and take the money back whenever you need it. All of that is true. What almost nobody explains is where the saved interest goes — because it does not go into shortening your loan, and the borrowers who assume it does spend years waiting for a maturity date that never moves.

What the account actually is

A normal home loan is a term loan. A fixed amount goes out, a fixed instalment comes back every month, and the outstanding falls along a schedule set on day one. Money only travels in one direction.

An overdraft-linked home loan replaces that with a running account. The loan still has an instalment and an end date, but the account behaves like a credit limit: you can put spare money in whenever you have it, and pull it back out whenever you need it. Interest is worked out daily on the net figure — what you owe, minus what you have parked. Leave five lakh in there for eleven days and you have genuinely saved eleven days of interest on five lakh, and you can take it back on the twelfth.

That is a real benefit and it is not a trick. The problem is that almost everything written about these accounts stops there, at the pleasant part, and the mechanics underneath are where borrowers get confused.

The three lines on your statement

Open the account online and you will see three figures rather than one outstanding balance. Everything that follows depends on knowing which of them is the loan.

Drawing power is the principal you still owe. It falls every month by the principal portion of your instalment, exactly as it would on an ordinary loan, and it is the ceiling on what you are allowed to withdraw.

Available balance is what you have parked, plus the interest you have saved so far. This is the withdrawable figure, and it is the one people watch.

Book balance is the drawing power minus the available balance, and it is usually displayed as a negative number, which unsettles people the first time they see it. It is the only figure that interest is charged on.

So a loan with sixteen lakh of drawing power and four lakh parked shows a book balance of twelve lakh, and interest that month is charged on twelve lakh, not sixteen. That much is intuitive. The next part is not.

Where the saved interest actually goes

Here is the mechanic that decides everything, and the one that product pages skip.

Your instalment does not change when you park money. It was fixed at sanction and it stays fixed. Inside it, the principal that comes off your drawing power also does not change — it follows the schedule drawn up on day one, month by month, as though you had parked nothing at all.

But the interest actually charged is smaller, because it was worked out on the book balance. The instalment is the same size, the principal slice is the same size, and the interest slice has shrunk. Something is left over. That leftover is not applied to your loan. It is credited into your available balance.

Read that again, because it is the whole article. The interest you save comes back to you as money you can withdraw, not as months removed from your loan. Your maturity date is exactly where it was. Your drawing power falls at exactly the rate it always would have. What grows is the pile of cash sitting against the loan — and it grows a little faster each month, because the bigger it gets, the more interest it saves, and that saving is credited back into it too.

This is why every page promising that these accounts "reduce your loan tenure" is describing something that does not happen on its own. The loan does end early in a sense — there comes a month when the available balance has grown to match the drawing power, the book balance hits zero, and you are paying no interest at all. At that point you can hand the parked money over and close the account. But that is a decision you make. Until you make it, the loan runs to its original end date with an instalment being debited every month, most of which is quietly being handed straight back to you.

The premium you pay on all of it

The second thing to understand is the price of the facility. Lenders do not offer a running account with unlimited free withdrawals out of generosity — these loans carry a higher rate than the plain term loan from the same lender to the same borrower. The gap is usually modest, in the region of a quarter to half a percent, and it varies by lender and by profile. Your sanction letter has the real number and it is worth finding before anything else.

The asymmetry is the point. That premium is charged on your entire outstanding, every day, whether the account holds five lakh or nothing. The saving is earned only on the slice you have parked. So the two only cancel out at a particular parked balance, and below it you are paying for a facility you are not using.

The balance where they meet is easy to state. Take the premium, divide it by the total overdraft rate, and apply that fraction to your outstanding. On a fifty lakh loan at eight percent with a premium of four-tenths of a percent, that fraction is 0.4 divided by 8.4 — a shade under five percent. Which means a shade under two lakh forty thousand has to be sitting in that account, on average, every single day, before the facility has earned back what it charges you.

Note the word average. A balance that peaks at six lakh the week the bonus lands and drains to forty thousand by March is not a six lakh parked balance; it is whatever it averaged across the year, and interest is charged daily, so the account keeps a very exact record of the difference. People who spend the money and refill it are frequently below the line without realising, because they remember the peak.

Park it, or prepay it

Set the two options side by side on the same loan and the trade becomes clear. Fifty lakh outstanding, twenty years to run, eight percent on the ordinary loan and eight-point-four on the overdraft version, with five lakh available either way.

Three things fall out of that table. The first is that both ways of using the five lakh are enormously better than doing nothing — around fourteen to sixteen lakh of interest, on a single decision about money you already had.

The second is that prepaying still wins on interest, by roughly a lakh and a half here. That is the price of the premium, and it is the honest answer to "which is cheaper". Spread across the years you actually hold the surplus it works out at something like eight hundred and fifty rupees a month. That is what you are paying to keep five lakh within reach — for a hospital admission, a redundancy, a fee that arrives without warning. Whether that is a good deal is a question about your life rather than your loan, and reasonable people answer it differently.

The third is the last row, and it is the one to take seriously. A borrower who takes the overdraft version and then never has meaningful surplus to park does not end up where they started. They end up three lakh worse off than the plain loan, because the premium ran for twenty years against a saving that never arrived. The facility is not free optionality. It is a paid subscription, and it is only worth the price if you use it.

What parked money does not do

A surplus sitting in the account is not a repayment, and the tax treatment follows that plainly. Only the principal and interest genuinely paid through your instalment count towards a claim. The interest certificate your lender issues at the end of the year captures those two figures and nothing else — the parked balance does not appear in it, because as far as the loan is concerned, no repayment happened.

This used to matter more than it does. The old argument for keeping a home loan running rather than clearing it was that the interest earned you a deduction, so the effective cost was lower than the headline rate. That argument has thinned considerably now that the new tax regime is the default and most salaried borrowers are on it, since the deductions that made the case simply are not available there. As covered in the piece on what changed for salaried filers, a great deal of planning built around the old regime quietly stopped applying to most people.

The practical consequence for this decision is a simplification. If the tax break is not in play, there is no tax reason to prefer keeping money in the loan over clearing the loan, and the choice between parking and prepaying comes down to exactly one question: how likely are you to need the money back?

The two traps worth knowing before you sign

The first catches buyers of under-construction property, and it catches them hard. On a loan released in stages against construction progress, the amount not yet paid to the builder sits inside your available balance. It is the same figure, on the same line, indistinguishable from your own parked money. A borrower who sees eleven lakh of available balance, of which nine is undisbursed loan waiting on the next slab, can very reasonably believe they have eleven lakh to draw on. They do not. Until the final disbursement is done, that portion is not withdrawable, and discovering this in the middle of an emergency is a bad way to learn it. If your loan is on a construction-linked plan, ask the lender in writing to confirm how much of the available balance is genuinely yours.

The second is smaller but catches people monthly. This is an overdraft account, not a savings account. Cash withdrawals carry charges, there is no interest-free window of any kind, and interest starts running the moment money leaves. It works well as a place to hold a sinking fund, an emergency buffer or a bonus you have not yet allocated, moved in and out by transfer. It works badly as the account your household spends from.

Who this is actually for

Put all of it together and the product sorts borrowers fairly cleanly.

It suits people whose income arrives lumpily — a variable component, an annual bonus, professional fees that land in clumps — and who therefore hold large balances for long stretches without being able to commit them permanently. It suits anyone who wants to keep a serious emergency fund but resents watching it earn a fraction of what their loan costs, because parking it against the loan effectively earns the loan rate, tax-free, with same-day access. And it suits borrowers who have a lump sum they may need back within a few years: a prepayment would be the cheaper choice if the money were truly spare, but it is not spare, and undoing a prepayment means applying for fresh credit at whatever rate exists then.

It does not suit a borrower whose salary is fully committed by the twentieth of every month. There will be no meaningful surplus to park, the premium will run for the full tenure regardless, and the plain term loan is straightforwardly cheaper. It also does not suit anyone who has the surplus, is confident they will never need it back, and simply wants the loan gone — for them the prepayment is both cheaper and one less account to manage, and as Part 6 of this masterclass sets out, the exit no longer carries a charge on most floating-rate loans to individuals.

The question to answer before signing is not whether the account is clever. It is whether you will genuinely keep a balance in it, month after month, larger than the break-even figure — and whether the access is worth what it costs. Both of those are answerable in advance with your own numbers, which is a far better position than finding out in year seven.

Written at the MoneyClarityTech desk — by a working retail-credit professional in Indian banking who reads loan files, credit reports and bank statements every working day. Patterns from hundreds of real cases; every identifying detail removed. More about MoneyClarityTech →