The standard advice is a one-liner: your home loan is at 8.5%, equity returns 11-12% over the long run, so never prepay - invest the surplus and let the gap compound in your favour. It sounds airtight and it is repeated everywhere. It is also often wrong, because it quietly assumes the entire interest you pay is tax-deductible. On a large home loan in the early years, most of it is not. The Section 24 cap of Rs. 2 lakh is where the clean story falls apart.
This post does the actual arithmetic. We take an 8.5% home loan, compute the real post-tax cost after the Section 24 deduction (not the fantasy version), compute the post-tax equity return, and find the exact breakeven: the equity return below which prepaying wins. The answer depends on your loan size, your tax bracket, and your regime, and it is more nuanced than either camp admits.
The naive rule of thumb, and where it breaks
The rule of thumb goes like this:
Effective loan rate = loan rate x (1 - marginal tax rate)
8.5% x (1 - 0.30) = 5.95%
At a 5.95% effective cost against 10-11% post-tax equity, investing wins by a mile. Case closed.
Except that formula assumes every rupee of interest earns you a tax deduction. Section 24(b) caps the interest deduction on a self-occupied home at Rs. 2 lakh per year. And it only exists in the old tax regime - under the new regime (the default since FY 2023-24), the Section 24 deduction on a self-occupied property is gone entirely, so your effective rate is simply 8.5%.
So the honest effective rate has three cases, not one:
- New regime: no deduction. Effective rate = 8.5%.
- Old regime, small loan: annual interest is below Rs. 2 lakh, fully deductible. Effective rate = 8.5% x (1 - tax) = 5.95% at 30%.
- Old regime, large loan: annual interest is well above Rs. 2 lakh, only Rs. 2 lakh is shielded, the rest is paid with post-tax money. Effective rate sits between the two.
Most borrowers who are told “your loan is really 5.95%” are in case 3 and paying a lot more than that.
What the Section 24 cap actually does
Take a Rs. 50 lakh loan at 8.5% over 20 years. The EMI is Rs. 43,391. In the first year, roughly Rs. 4.2 lakh of your EMIs is interest and only about Rs. 0.99 lakh is principal (this is why early prepayment is so powerful - you are killing the most interest-heavy years).
Now apply Section 24. You paid Rs. 4.2 lakh in interest but can deduct only Rs. 2 lakh. In the 30% bracket that deduction saves you Rs. 60,000 in tax. Your real interest cost for the year is Rs. 4.2 lakh minus Rs. 0.6 lakh = Rs. 3.6 lakh. As a rate on the outstanding, that is about 7.3%, not 5.95%.
Here is the effective rate at an 8.5% coupon, 30% bracket, old regime, in the first full year, by loan size:
| Loan size | Year-1 interest (approx) | Deductible | Tax saved (30%) | Effective rate |
|---|---|---|---|---|
| Rs. 20 lakh | Rs. 1.69 lakh | Rs. 1.69 lakh (full) | Rs. 50,700 | ~5.95% |
| Rs. 30 lakh | Rs. 2.53 lakh | Rs. 2.00 lakh (capped) | Rs. 60,000 | ~6.5% |
| Rs. 50 lakh | Rs. 4.22 lakh | Rs. 2.00 lakh (capped) | Rs. 60,000 | ~7.3% |
| Rs. 75 lakh | Rs. 6.33 lakh | Rs. 2.00 lakh (capped) | Rs. 60,000 | ~7.8% |
| Rs. 50 lakh (new regime) | Rs. 4.22 lakh | Rs. 0 | Rs. 0 | 8.5% |
Two things jump out. First, the bigger the loan, the closer the effective rate creeps back toward the full 8.5%, because the Rs. 2 lakh shield is a fixed crumb against a growing interest bill. Second, the shield also shrinks over time on any loan: as the balance falls and annual interest drops below Rs. 2 lakh, the loan slides into the “fully deductible” zone and the effective rate falls to 5.95%. On a Rs. 50 lakh loan at 8.5%, annual interest drops below Rs. 2 lakh only around year 13-14. For most of the life of a large loan, you are much nearer 7.3% than 5.95%.
There is also a Rs. 1.5 lakh Section 80C deduction on principal repaid, but 80C is almost always already exhausted by EPF, insurance premiums and ELSS, so the marginal home loan principal usually buys no extra tax benefit. I am ignoring it here, which is the realistic assumption for most salaried borrowers.
The investment side, after tax
Equity index funds and large-cap funds have historically delivered roughly 11-12% CAGR over 10-year-plus holding periods in India. These are historical, representative figures, not a promise - the next decade could be lower.
The tax drag is lighter than most people fear. Long-term capital gains on equity are taxed at 12.5% on gains above Rs. 1.25 lakh per financial year. Over a long SIP the effective drag works out to roughly 1 to 1.5 percentage points, so 11% pre-tax becomes about 9.5-10% post-tax.
| Instrument | Pre-tax | Post-tax (approx) |
|---|---|---|
| Nifty 50 index fund | 11-12% | 9.5-10.5% |
| Flexi-cap / large-cap fund | 11-13% | 9.5-11% |
| PPF | 7.1% | 7.1% (tax-free) |
| FD | 7-7.5% | 4.9-5.25% (30% bracket) |
The comparison that matters: prepayment is a guaranteed, tax-free return equal to your effective loan rate. Every FD or debt fund you might hold instead yields less than that post-tax. So the choice is never “prepay vs FD” - prepaying always beats parking money in debt. The only real contest is prepay vs equity.
The breakeven: a 10-year worked comparison
Say you have Rs. 20,000 a month of genuine surplus for 10 years, and a Rs. 50 lakh loan at 8.5% (old regime, 30% bracket, effective rate ~7.3%).
Option A - invest the Rs. 20,000 in an equity SIP. Future value of Rs. 20,000/month for 120 months:
At 11% pre-tax: ~Rs. 43.4 lakh (invested Rs. 24 lakh, gain Rs. 19.4 lakh)
LTCG tax ~Rs. 2.3 lakh -> net ~Rs. 41.1 lakh
Option B - prepay the Rs. 20,000 every month. Each prepayment earns you the effective loan rate, guaranteed and tax-free. The equivalent corpus is the future value at 7.3%:
At 7.3%: ~Rs. 35.2 lakh (all of it "tax-free", it is debt you no longer owe)
At an 11% equity return, investing wins by about Rs. 6 lakh over the decade. That is the case for “never prepay” and, if equity delivers, it is real.
But run the SIP at a lower assumed return and the gap closes fast:
| Assumed equity return (pre-tax) | SIP corpus, post-tax | Prepay-equivalent corpus | Winner |
|---|---|---|---|
| 12% | ~Rs. 43.3 lakh | Rs. 35.2 lakh | Invest, by ~Rs. 8 lakh |
| 11% | ~Rs. 41.1 lakh | Rs. 35.2 lakh | Invest, by ~Rs. 6 lakh |
| 9% | ~Rs. 37.7 lakh | Rs. 35.2 lakh | Invest, by ~Rs. 2.5 lakh |
| 8% | ~Rs. 35.2 lakh | Rs. 35.2 lakh | Dead heat |
| 7% | ~Rs. 33.0 lakh | Rs. 35.2 lakh | Prepay, by ~Rs. 2 lakh |
So the breakeven pre-tax equity return, for this large-loan, old-regime, 30% case, is about 8%. Above it, invest. Below it, prepay. The extra point over the 7.3% loan rate is the LTCG tax you pay on the equity side.
The breakeven by scenario
Repeating that exercise across the cases gives a compact map. “Breakeven equity return” is the pre-tax equity CAGR below which prepaying the 8.5% loan wins:
| Your situation | Effective loan rate | Breakeven equity return | Practical read |
|---|---|---|---|
| New regime (any loan) | 8.5% | ~10% | Very close call; lean invest only if bullish |
| Old regime, Rs. 75 lakh loan, 30% | ~7.8% | ~9% | Slight edge to invest |
| Old regime, Rs. 50 lakh loan, 30% | ~7.3% | ~8% | Invest, with margin |
| Old regime, Rs. 30 lakh loan, 30% | ~6.5% | ~7.5% | Invest clearly |
| Old regime, small/aged loan, full shield | ~5.95% | ~7% | Invest strongly |
| Old regime, Rs. 50 lakh loan, 20% bracket | ~7.6% | ~8.5% | Invest, thinner margin |
The headline: on the naive 5.95% number, equity wins in a landslide. On the honest number for a large loan in the new regime, the breakeven is around 10% pre-tax, which is right in the middle of what equity has historically delivered. That is no longer a slam dunk - it is a genuine coin toss that depends on your return assumption and your stomach for risk.
Why the guaranteed-vs-risky gap matters more than the spread
The tables above compare an average equity return to a certain loan rate, but they are not the same kind of number. The prepayment return is locked in. The equity return is a range that includes a real chance of the market being flat or down over any given decade - Indian equity has had 10-year windows below 8% CAGR.
A rational way to price that is: demand a risk premium of 2-3 percentage points before choosing the risky option. If your effective loan rate is 8.5% (new regime), you would want to expect roughly 10.5-11.5% from equity just to be compensated for the uncertainty. That pushes the new-regime borrower firmly toward prepayment, or at least toward a split.
For an old-regime borrower with a genuinely low effective rate of 6-6.5%, the premium is easily cleared and investing is the sound call.
The hybrid that usually wins in practice
You rarely have to pick one. The order of operations that suits most borrowers:
- Emergency fund first. Six months of expenses in a liquid fund or sweep-in FD before a single rupee goes to prepayment or equity SIP. A big loan with no buffer forces you onto a credit card at 40% the first time life goes wrong.
- Grab the Section 24 shield. If you are in the old regime, make sure your annual interest at least reaches Rs. 2 lakh so the deduction is fully used before you accelerate prepayment. Do not prepay so aggressively in the early years that you shrink your own tax benefit.
- Split the surplus. For a large loan where the breakeven is close (new regime, or old-regime loans above Rs. 50 lakh), a 50-50 split of the surplus between an equity SIP and annual prepayments hedges your bets: you capture most of the equity upside while steadily de-risking the debt.
- Prepay early, not late. If you do prepay, do it in the first 5-7 years when the interest component of the EMI is highest. A prepayment in year 3 saves far more interest than the same rupee in year 15. And instruct the bank to reduce tenure, not EMI, to maximise interest saved.
- Reassess when rates move. If the loan resets to 9.5% or higher, the effective rate rises and the case for prepayment strengthens. If it drops toward 8% or below, tilt back to investing.
Bottom line
Prepay when your honest effective loan rate is close to what you realistically expect from equity, and that happens more often than the “always invest” crowd admits. On the new regime, where Section 24 gives you nothing, your 8.5% loan costs a full 8.5% and prepaying is close to a wash with equity - lean toward prepaying or splitting. On the old regime with a large loan, the Rs. 2 lakh cap means your effective rate is around 7.3-7.8%, not the 5.95% you were sold, and the breakeven equity return is about 8-9%; investing still edges ahead but the margin is thinner than advertised. Only on a small or aged old-regime loan with the full deduction does the classic “never prepay” advice clearly hold. Whatever you choose, build the emergency fund first, use up the Section 24 shield before accelerating, and if you prepay, do it early and against the tenure.
These figures are illustrative and based on historical and representative numbers, not a forecast or investment advice - run your own loan schedule and tax situation before deciding.
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