Your Equity SIP's Real Return: Modelling Post-Tax CAGR After the New 12.5% LTCG Rule

Most investors track their equity SIP by its headline XIRR: the app shows 12%, and that number becomes the story. But the return you actually keep is the one measured after the taxman takes a slice at redemption. Since 23 July 2024, that slice on long-term equity gains is fixed at 12.5% under Section 112A of the Income-tax Act 1961, up from the old 10%, with the annual exemption held at Rs 1,25,000. The result is a quiet but permanent wedge between your gross XIRR and your true post-tax CAGR, and on a 15-year corpus that wedge runs into lakhs.

This piece models that wedge in rupee terms, using the Oquilia post-tax methodology anchored to Section 112A, and then sets an equity SIP side by side with a Public Provident Fund account paying 7.1% for Q1 FY 2025-26. The goal is a single, honest comparison for a long-horizon wealth target: growth-with-tax versus guaranteed-and-tax-free. You can reproduce every figure here in the LTCG-equity calculator and the SIP calculator.

Side-by-Side Comparison

Consider a Rs 25,000 monthly SIP into a diversified equity fund, run for 15 years at an illustrative 12% gross XIRR. Total invested is Rs 45,00,000 across 180 instalments. At 12% the corpus grows to roughly Rs 1,24,89,500, so the embedded long-term gain is about Rs 79,89,500. Redeem the whole holding in a single financial year and only Rs 1,25,000 of that gain escapes tax; the remaining Rs 78,64,500 is taxed at 12.5%, a bill of Rs 9,83,063. The net corpus lands near Rs 1,15,06,437. That single levy trims an illustrative 12% gross XIRR to a post-tax CAGR a little above 11% once you re-run the cash flows through the XIRR calculator.

Now compare that with a PPF account funded at the Rs 1,50,000 annual ceiling for the same 15 years. PPF pays 7.1% (Q1 FY 2025-26) and is EEE: the contribution qualifies under Section 80C, the interest is exempt, and the maturity is tax-free. Because nothing is taxed at exit, PPF's post-tax return equals its headline 7.1%. The equity SIP therefore keeps its lead even after the 12.5% haircut, but it carries market risk that PPF, backed by a sovereign guarantee, does not.

The table makes the trade-off explicit. Over 15 years the equity route delivers a materially larger corpus even after Section 112A tax, but the entire return is conditional on the market and on the investor's own behaviour during drawdowns. PPF hands over a smaller, certain sum. For the same Rs 1,50,000 a year, the choice is not really equity versus PPF but how much of the goal you are willing to leave exposed to a 30% to 40% temporary decline, the kind Indian equity has historically seen in bad years.

It is worth stressing how sensitive the post-tax gap is to the redemption pattern. In the single-year exit above, the Rs 1,25,000 exemption offsets barely 1.6% of a Rs 79,89,500 gain, so almost the entire gain is taxed at 12.5%. Split the same redemption across five financial years and you claim the Rs 1,25,000 exemption five times over, sheltering Rs 6,25,000 of gains instead of Rs 1,25,000 and cutting the tax bill by roughly Rs 62,500 for no change in the underlying investment. The lesson is that on equity, when you sell is now a tax decision as much as a market one, and a staggered redemption is the default a tax-aware investor should model first.

Tax Treatment

The tax rules that create the gross-to-net wedge are precise, and the holding-period boundary is where most investors slip. For listed equity and equity mutual funds, a holding of 12 months or less is short-term, taxed at a flat 20% under Section 111A since 23 July 2024. A holding of more than 12 months is long-term, taxed at 12.5% under Section 112A on gains above the Rs 1,25,000 annual exemption, with no indexation available. The worked example is simple arithmetic: Rs 5,00,000 of realised LTCG minus the Rs 1,25,000 exemption leaves Rs 3,75,000 taxable, and at 12.5% that is Rs 46,875 of tax.

Two nuances matter for a SIP specifically. First, every instalment carries its own 12-month clock, so a redemption is almost always a blend of long-term and short-term units unless you have paused contributions for over a year. That is why disciplined investors redeem oldest-units-first and why the XIRR concept beats a naive average return for measuring what you kept. Second, the Section 87A rebate, worth up to Rs 60,000 in the new regime for FY 2025-26, does not shelter Section 112A gains; the rebate applies to tax on normal income, while LTCG tax stands separately. For high earners, the surcharge on both 111A and 112A gains is capped at 15% even where slab income would attract more, and a 4% health and education cess sits on top. These rates are published at incometax.gov.in and should be checked before any large redemption.

A further point on cost base: the grandfathering relief from the 2018 reform still applies, so for units acquired before 31 January 2018 the cost is stepped up to the higher of actual cost or the 31 January 2018 fair market value. For anything bought since, cost is simply what you paid. Because indexation was withdrawn for equity, there is no inflation adjustment to soften the 12.5% rate, which is precisely why an inflation-adjusted view of the corpus matters and why the LTCG-equity calculator reports gains gross of any indexation benefit.

Who Should Pick Which

The right answer depends less on the products and more on the investor's horizon, risk appetite, and tax position. Three profiles cover most readers.

The long-horizon accumulator, saving for a goal 12 to 15 years out, should lean equity. Even after the 12.5% Section 112A levy, an illustrative 12% gross SIP compounds to a post-tax CAGR near 11%, comfortably above PPF's tax-free 7.1%. AMFI data shows the retail SIP habit is now structural rather than fashionable, with the industry SIP book crossing Rs 15 lakh crore, so this investor is in large company. The practical discipline is to keep contributing through drawdowns and to redeem in tranches rather than one lump, which preserves the annual Rs 1,25,000 exemption across multiple financial years.

The capital-protection saver, or anyone within five years of the goal, should tilt toward PPF and other guaranteed instruments. A 20% STCG hit under Section 111A on any units sold inside 12 months, plus the risk of redeeming into a falling market, can wipe out years of equity's headline advantage. For this profile, PPF at 7.1% tax-free is often a better risk-adjusted outcome than chasing an equity return that may not survive a bad exit year.

The tax-aware optimiser should use both, and should actively harvest. By booking roughly Rs 1,25,000 of long-term gains each financial year and immediately reinvesting, this investor resets the cost base and uses an exemption that would otherwise lapse. Over a 15-year SIP, systematically harvesting the annual exemption can meaningfully cut the terminal tax bill compared with a single redemption; the tax-harvesting calculator quantifies the saving for a given corpus. This is the profile for whom the gap between gross XIRR and post-tax CAGR is smallest, because they manage the tax event rather than letting it happen all at once.

A note on debt-style alternatives: since 1 April 2023, most debt mutual funds are taxed at slab rates with no LTCG concession, which is why equity funds, even at 12.5%, retain a structural tax edge for growth goals. That edge, and the certainty of PPF, are the two poles this comparison sits between. Data from amfiindia.com underlines the direction of travel: SIP inflows have become the ballast of the domestic fund industry, and the 12.5% rule does nothing to change the arithmetic that, over long horizons, equity still out-earns fixed income after tax.

FAQ

Is the Rs 1.25 lakh LTCG exemption available every financial year?

Yes. Under Section 112A, the first Rs 1,25,000 of long-term gains from listed equity and equity mutual funds is exempt in each financial year. The exemption is per person, does not carry forward, and lapses if unused, which is the entire logic behind staggered redemptions and annual harvesting.

What is the difference between STCG and LTCG on equity funds?

Holding period decides it. Units held 12 months or less are short-term and taxed at 20% under Section 111A. Units held more than 12 months are long-term and taxed at 12.5% under Section 112A on gains above Rs 1,25,000 a year, with no indexation. Both rates took effect on 23 July 2024.

Can I claim the Section 87A rebate against my equity LTCG?

No. The Section 87A rebate, up to Rs 60,000 in the new regime for FY 2025-26, reduces tax on your normal income only. The special-rate tax on Section 112A long-term gains is computed separately and is not covered by the rebate.

Does the 12.5% rate apply to SIP units bought before 23 July 2024?

Any gain realised on or after 23 July 2024 is taxed at the 12.5% long-term rate, whatever the purchase date, provided the holding exceeds 12 months. Each SIP instalment runs its own 12-month clock for the short-term versus long-term test.

How does PPF compare with an equity SIP after tax?

PPF returns 7.1% for Q1 FY 2025-26 and is fully tax-free, so its post-tax return equals its headline rate. An equity SIP at an illustrative 12% gross falls to roughly 11% post-tax after the Section 112A levy, keeping its lead over PPF but adding market risk and no capital guarantee.

Is there a surcharge on equity capital gains for high earners?

Surcharge kicks in above Rs 50 lakh of total income, but for Section 111A and 112A gains it is capped at 15% regardless of the slab-level surcharge on other income. A 4% health and education cess applies on the tax plus surcharge.

How do I estimate my own post-tax SIP return?

Compute the tax on your realised gains in the LTCG-equity calculator, subtract it from your corpus, then feed the net figure and your instalment dates into the XIRR calculator. The distance between your gross XIRR and that post-tax CAGR is the real cost of the 12.5% rule for your portfolio.