Advance Tax Trap: Why Salaried Employees with Capital Gains or Rent Owe 234B Interest

Your employer deducts TDS on every salary credit, and for most people that is the entire tax story. So the natural assumption is that if you are salaried, the tax department is already fully paid and you have nothing to do except file a return. That assumption is wrong the moment a second stream of income shows up, and the two most common second streams for salaried people are exactly the ones nobody withholds tax on: capital gains from selling shares or mutual funds, and rent from a flat.

The tax on that second income is real, and the department wants it in four installments during the year, not in one lump at filing time. Pay it late and you are charged interest under Sections 234B and 234C at 1% per month. It is not a penalty you can argue down, it is not discretionary, and the software computes it automatically the second you enter your numbers in the ITR. This post shows you the actual rupee cost on ₹1 lakh of tax you should have paid as advance tax, and the exact steps to never pay it again.

Why salary TDS does not cover you

TDS on salary is calculated by your employer on your salary alone. Your employer has no idea you sold ₹8 lakh of an equity fund in September or that you rent out a 2BHK in Pune. Unless you formally declare that other income to your payroll team (most people do not, and payroll often will not adjust for capital gains anyway), the TDS on your Form 16 is short by exactly the tax on that other income.

The law says that if your total tax liability after TDS is ₹10,000 or more in a financial year, you must pay the balance as advance tax during the year. That threshold is trivially crossed. Here is what commonly triggers it for a salaried person:

• Equity LTCG above the ₹1.25 lakh annual exemption, taxed at 12.5%.
• Equity STCG, taxed at 20%.
• Rental income, taxed at your slab rate after the 30% standard deduction and home loan interest.
• Freelance or consulting income, taxed at slab rate.
• Interest above what TDS covered, dividends above ₹10,000, or a large FD maturing.

Any one of these can leave you with a tax gap that TDS never touched. That gap is what advance tax is for.

The four due dates

For an individual, advance tax is due in four installments across the financial year. The percentages are cumulative.

Note there is no installment on 31 March. If you have not paid 100% by 15 March, you are already exposed. And “total tax” here means your whole liability net of TDS, including the tax on capital gains and rent.

The two interest sections, plainly

Section 234C punishes you for missing the installment schedule. It charges 1% per month on the shortfall in each installment, for a fixed number of months per installment (three months each for the first three, one month for the last). It runs during the financial year.

Section 234B punishes you for not paying at least 90% of your total tax by 31 March. It charges 1% per month on the unpaid amount, starting 1 April of the assessment year and running until you actually pay, usually at filing time. Any part of a month counts as a full month.

They stack. 234C is the in-year penalty for bad timing, 234B is the after-year penalty for still being short. You can easily pay both on the same rupee of tax.

The actual math on ₹1 lakh of unpaid advance tax

Take a concrete case. FY 2025-26. You are salaried, TDS on salary is fully paid, but you have ₹1,00,000 of tax due on non-salary income (say rent plus some equity STCG) that you paid nothing towards during the year. You clear the full ₹1 lakh only when you file, on 31 July 2026.

Section 234C, installment by installment

Because this income was known through the year (rent and regular gains), the full installment schedule applies. Shortfall is measured against each cumulative deadline, and you paid zero.

That is ₹5,050 in 234C interest, locked in before the financial year even ends.

Section 234B, until you pay

You paid 0% of your tax by 31 March, well under the 90% threshold, so 234B applies on the full ₹1,00,000. It runs from 1 April 2026 to the month you pay. You pay on 31 July 2026, which is April, May, June, July, four months.

234B = ₹1,00,000 x 1% x 4 months = ₹4,000

The combined bill

So ₹1 lakh of tax you deferred cost you ₹9,050 in interest over roughly nine months, from the June installment clock through to a July filing. That is an effective annualised cost of well above 12%, and every extra month you delay filing adds another ₹1,000 in 234B. Drag payment to December 2026 instead of July and 234B alone becomes ₹9,000, pushing the total past ₹14,000.

The uncomfortable part: on the same ₹1 lakh, you are being charged twice for the last stretch of the year. 234C already billed you for the March shortfall, and 234B bills you again from April onward. That overlap is legal and intended.

The capital gains escape hatch most people miss

Here is the one nuance worth real money. Section 234C has a proviso: interest is not charged on a shortfall that arose because of capital gains (or dividend income, or casual income like lottery), provided you pay the tax on that gain in the remaining installments, or by 31 March if the gain came after 15 March.

In plain terms: if you sell shares in November and book a large LTCG, you are not expected to have pre-paid tax on it in the June and September installments. As long as you pay that gain’s tax in the December and March installments, 234C does not touch it. This is why the “known through the year” assumption matters in the table above. Pure lumpy capital gains often escape 234C entirely.

But, and this is the trap, 234B has no such proviso. Even if 234C forgives your November capital gain, 234B still expects 90% of your total tax, capital gains included, paid by 31 March. Miss that and 234B runs on the full amount from 1 April regardless. So a salaried investor who books a big gain in March, does nothing, and pays at filing dodges 234C on that gain but walks straight into 234B.

The rule of thumb people repeat is “capital gains are exempt from advance tax interest.” That is half true and dangerous. The correct version: capital gains get relief from 234C timing, never from the 234B year-end 90% test. If you realise a gain, pay the tax on it in the very next installment. If you realise it after 15 March, pay it by 31 March by self-assessment challan.

Who is actually exempt

Two genuine exemptions, so you do not overpay out of fear.

• Resident senior citizens (60+) with no business or professional income are exempt from advance tax entirely under Section 207. A retired person living on pension, rent, and capital gains simply pays everything as self-assessment tax at filing with no 234B or 234C. This is a real and underused relief.
• Presumptive taxpayers under 44AD (small business) or 44ADA (professionals, freelancers) can pay their entire advance tax in a single installment by 15 March instead of four. A freelancer opting for 44ADA does not need to worry about the June, September, and December dates, only the March one.

If you are salaried and under 60 with capital gains or rent, neither exemption helps you. You are on the four-installment schedule.

How to pay and where it goes in the ITR

Paying advance tax takes about five minutes and needs no chartered accountant.

1. Go to the income tax e-filing portal, e-Pay Tax.
2. Choose the assessment year and select minor head 100 (Advance Tax) for in-year payments. After the financial year ends, the same balance is paid as minor head 300 (Self-Assessment Tax).
3. Pay via net banking or UPI. You get a challan with a BSR code, challan serial number, and date. Save it.

When you file your ITR, these numbers go in specific schedules:

• Schedule IT captures each advance tax and self-assessment challan: BSR code, date, serial number, amount. This is what credits your payments against the computed tax.
• Schedule CG reports capital gains, split by asset type and, for equity, by the 12.5% LTCG and 20% STCG rates. The ₹1.25 lakh LTCG exemption is applied here.
• Schedule HP reports house property income: gross rent, minus municipal taxes, minus the 30% standard deduction, minus home loan interest.
• Part B-TTI is where the software totals your tax and, critically, computes 234B and 234C automatically from your challan dates. If you paid on time, these lines read zero. If you did not, you see the interest and pay it as part of self-assessment before submitting.

The playbook for next financial year

The whole trap is avoidable with one habit: estimate your non-salary tax early and pay it on the installment dates.

1. In April, estimate. Rough out your likely rent for the year and any gains you have already booked. Multiply expected rental income (post 30% deduction and loan interest) by your slab rate, and expected equity gains by 12.5% or 20%.
2. Pay 15% by 15 June, 45% by 15 September, 75% by 15 December, 100% by 15 March, on the base you can reasonably foresee. For rent and freelance income this is easy because it is predictable.
3. For each lumpy capital gain, pay its tax in the next installment after you book it. Sold a fund in August? Include that tax in the September installment. This satisfies the 234C proviso and, more importantly, keeps you above the 90% line for 234B.
4. True up by 15 March. Add up everything realised through the year and make sure cumulative advance tax is at least 90% of total tax. If a gain landed after 15 March, clear it by 31 March by self-assessment.
5. Keep every challan. You will need the BSR code and serial number for Schedule IT.

The mental model that keeps you out of trouble: the day money that is not salary hits your account and is taxable, some fraction of it already belongs to the government, and the clock on that fraction is running.

Bottom line

If you are salaried and you booked equity gains above ₹1.25 lakh, collected rent, or earned freelance income, your salary TDS does not cover you and the advance tax obligation is yours. On ₹1 lakh of deferred tax, expect roughly ₹9,000 in combined 234B and 234C interest if you settle at a July filing, and ₹1,000 more for every month you delay beyond that. Capital gains get you off the 234C timing hook only, never the 234B year-end test, so pay the tax on any gain in the very next installment. Set four calendar reminders for 15 June, 15 September, 15 December, and 15 March, estimate in April, pay through the year, and the interest lines in your ITR stay at zero.

Figures here are illustrative and use FY 2025-26 rates. This is not investment or tax advice; confirm your own numbers before filing.