A small post-filing demand of ₹100 to ₹5,000 is usually one of three things: s.140A interest on a self-assessment balance you underpaid, rounding, or a minor TDS mismatch — and your move is to pay it via challan ITNS 280 code 400 within 30 days to stop s.220(2) interest at 1% per month, or file a rectification u/s 154 if the CPC added something that is factually wrong. What it almost never is — for a small amount — is a genuine mistake that needs a revised return; s.139(5) is for under/over-reporting income, not for paying a small balance you already knew about.

What s.140A requires

Section 140A requires that before you file your return, you compute your tax, deduct TDS/advance-tax credits, and pay the balance as self-assessment tax. The catch for most filers: if your estimate is short, the shortfall does not vanish at filing — interest runs on it.

Post Finance Act 2022, s.140A(3) is not itself a charging provision — it simply deems interest under s.234A/234B/234C to be self-assessment tax payable alongside the tax at filing. So the 1% per month charge on any shortfall traces to s.234A (return-delay) / s.234B (advance-tax shortfall) / s.234C (instalment deferment), not s.140A(3) as a separate layer.
For a salaried filer where advance tax + TDS ≥ 90% of assessed tax (100% for companies), s.234B does not kick in at all; and no advance tax is due where the balance-tax-payable-after-TDS is below ₹10,000 (s.208). s.234B runs from 1 April of the AY to the date of payment/filing.
The CPC computes all of this at processing and raises the balance in the 143(1) intimation.

Why the demand is usually small — the three causes

Cause	What happened	The fix
140A interest	You paid the tax balance but slightly late / slightly short; interest on the difference	Pay the demand; it is computation, not error
Rounding	Payment rounded down from the exact balance, leaving a small shortfall (s.288B rounds income and tax to the nearest ₹10 — never more than ₹5 either way)	Pay it; trivial but an open line attracts s.220(2) interest
Minor TDS mismatch	A claimed credit did not match 26AS (late posting or a few hundred rupees)	Check 26AS; if the credit posted later, file a rectification u/s 154

If the amount is a few hundred rupees, the cheapest path is usually to pay it and move on — the cost of disputing exceeds the demand. If it is thousands and clearly wrong (a TDS credit that 26AS confirms), rectify.

Pay, rectify, or revise? The decision rule

Situation	Route
The demand is correct (interest/rounding)	Pay — challan ITNS 280, major head 0021, code 400, within 30 days
The CPC made a factual error (TDS denied despite 26AS showing it)	Rectify u/s 154 with the 26AS extract
You under/over-reported actual income (missed a capital gain, claimed a wrong deduction)	Revise u/s 139(5) — only if the return itself was wrong, not just the tax balance
You dispute the whole demand	Appeal u/s 246A (Form 35, within 30 days) — rarely worth it for a small amount

A revised return is for wrong income, not wrong arithmetic on the tax balance. If the only issue is that you paid less self-assessment tax than due, the correct response is to pay the shortfall — a revised return does not erase s.140A interest that already accrued.

Worked example: Ayesha's ₹5,150 demand

Persona: Ayesha, salaried, files her AY 2026-27 ITR in July 2026, paying ₹12,000 as self-assessment tax.

The intimation: a 143(1) demand of ₹5,150 — ₹5,000 shortfall plus ₹150 interest.

Step 1 — Diagnose. Ayesha opens the intimation. The ₹5,000 is a TDS credit she claimed that 26AS did not yet show (her employer's March-quarter TDS posted after she filed); the ₹150 is s.140A interest on the shortfall.

Step 2 — Verify against 26AS. The ₹5,000 TDS is genuinely hers — it appears in 26AS now.

Step 3 — Rectify, don't pay. Because the shortfall is a data-timing issue (the credit exists), Ayesha files a rectification u/s 154 with the 26AS extract showing the ₹5,000 posting. The CPC re-processes and restores the credit — the ₹5,000 and the ₹150 interest on it fall away.

Step 4 — If it had been a real shortfall. Had the ₹5,000 been an actual underpayment (no TDS to support it), Ayesha would pay the ₹5,150 via challan 280 code 400 within 30 days — a revised return would not remove the interest already accrued under s.140A.

The takeaway: for a small demand, first ask is the money actually mine (26AS check). If yes → rectify. If no → pay. Revise only when the income itself was wrong.

Changed FY 2025-26: No change to s.140A. The change is in what creates the small demands — AIS-driven TDS reconciliation is now automatic at processing, so a short self-assessment that once went unnoticed is computed with interest on the books. Pay the correct balance at filing and the demand never arises.

The mistakes that create small demands

Most tiny post-filing demands trace to one of four filing habits:

Guessing the TDS total. Claiming a credit that 26AS does not yet show creates a shortfall with 140A interest. Check 26AS before you claim.
Rounding the self-assessment. Paying ₹12,000 when the correct balance is ₹12,478 leaves ₹478 plus interest on the books.
Ignoring advance tax. A salaried person whose employer TDS covers salary but who has side income (crypto, F&O, interest) short-pays because the employer never saw the side income.
Filing the wrong form. A wrong ITR form creates a defective return and, with it, interest and fee lines that a correct form would not have.

Each is avoidable at filing time; each becomes a 143(1) line after it.

Frequently asked questions

1. What is self-assessment tax under s.140A?

The balance of tax you must pay before filing your return — your total tax less TDS and advance-tax credits. A shortfall attracts interest.

2. Why did I get a small demand after filing?

Usually s.140A interest on a short self-assessment, rounding, or a minor TDS mismatch — not an error in the income you reported.

3. What is the interest on an underpaid self-assessment?

1% per month on the shortfall, charged under s.234A / s.234B / s.234C (post Finance Act 2022, s.140A(3) merely deems these to be self-assessment tax payable at filing — it does not itself charge interest).

4. Should I pay a ₹500 demand or dispute it?

Pay it if it is correct (interest/rounding). The cost and time of disputing a small amount exceed the demand. If it is factually wrong (TDS denied despite 26AS), rectify u/s 154.

5. When should I file a revised return u/s 139(5)?

When the income itself was wrong — missed income, a wrong deduction, a wrong form. Not for a small balance on the tax computation.

6. Does a revised return remove self-assessment interest?

No. Interest under s.140A already accrued on the shortfall; a revised return changes the income but does not retroactively erase the interest period.

7. How do I pay the demand?

Via challan ITNS 280, major head 0021, code 400, within 30 days of the intimation, to avoid interest under s.220(2) at 1% per month.

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Last verified: 2026-08-08 (FY 2025-26 / AY 2026-27)

Sources: s.140A(1)–(3) (self-assessment and interest), s.139(5) (revised return), s.143(1) (processing), s.154 (rectification), s.220(2) (interest on unpaid demand), s.234B/234C (advance-tax interest), s.288B (rounding), Challan ITNS 280 / code 400, Income-tax Act, 1961. s.140A interest period flagged [VERIFY]. For a personalised read on a notice, use the Notice Explainer.

Topics:section 140Aself-assessment taxdemand after filingrevised return

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