When you owe advance tax as an NRI, and the interest that follows

Advance tax is due when your Indian tax liability, after the TDS already deducted, comes to ₹10,000 or more in the financial year (Section 208). It is paid in four instalments through the year: 15% by 15 June, 45% by 15 September, 75% by 15 December and the whole by 15 March, each figure being the cumulative amount that should have been paid by that date.

For most NRIs, TDS handles the tax on routine income, so advance tax does not arise. It bites when TDS falls short: a buyer who under-deducted on a sale, rental income with too little withheld, or a gain no one deducted on at all. When the withheld tax does not reach your real liability, the balance is advance tax, and paying it on the instalment dates is what avoids the interest below.

There is a fair rule for income you could not have predicted. Under the proviso to Section 234C, where you fell short on the earlier instalments because of a capital gain, or certain other one-off income like a large dividend, that arose only later in the year, you are not charged the 234C instalment-shortfall interest on those earlier instalments, provided you pay the full tax on that gain in the instalment falling due after it arose, or, if no instalment is left, by 31 March.

So an NRI who sells a property in February and pays the tax on the gain by 15 March, or 31 March, is not penalised under 234C for not having paid it in the June or September instalments, because the gain had not yet happened then. This is genuine relief, and it means a late-year sale does not automatically carry instalment interest.

Here is the part that catches people. The 234C relief above deals only with the instalment-shortfall interest. It does not touch Section 234B, which is a separate charge: if the total advance tax you paid during the year is less than 90% of your finally assessed tax, interest at 1% a month runs from 1 April of the assessment year until you pay, regardless of the 234C relief.

So on that February property sale, if the buyer under-deducted and you did not pay the balance as advance tax by year end, you can still face 234B interest even though 234C was waived. The two are independent, and this is exactly the common NRI trap: assuming TDS covered a sale, discovering it did not, and finding interest has been accruing. A practising CA computes the real liability, times the advance-tax payment to use the 234C relief, and minimises the 234B exposure.