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Chapter XV - Return of Income

Section 266

Section 266: self-assessment

Section 266 requires taxpayers to settle up before they file: if tax is still payable after accounting for TDS, advance tax and other credits, the assessee must pay that tax - along with any interest and fee for delay - before furnishing the return under Section 263, 268, 280 or 294, and attach proof of payment.

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Need advice on Section 266?

This article is for general information. Refer to the Income-tax Act, 2025 as amended by the Finance Act, 2026 and the Taxation and Other Laws (Amendment) Act, 2026 for the official provisions. If you need professional advice for your situation, contact Bizeneed.

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Statutory text

Bare law

(1) Where, after taking into account the amounts referred to in subsection (2), any tax is payable on the basis of any return required to be furnished under section 263 or 268 or 280 or 294, then–– (a) the assessee shall be liable to pay such tax together with interest and fee payable under any provision of this Act for any delay in furnishing the return or any default or delay in payment of advance tax, before furnishing the return; and (b) the return shall be accompanied by proof of payment of tax, interest and fee.

(2) The amounts referred to in sub-section (1) shall be,— (a) the amount of tax, if any, already paid under any provision of this Act; (b) any tax deducted or collected at source; (c) any relief of tax claimed under section 157; (d) any relief of tax or deduction of tax claimed under section 159(1) or 160 on account of tax paid in a country outside India; (e) any relief of tax claimed under section 159(2) on account of tax paid in any specified territory outside India referred to in that section; (f) any tax credit claimed to be set off as per section 206(2)(e) to (h) and 206(3) and (4); and (g) any tax or interest payable according to the provisions of section 391(2).

(3) Where the amount paid by the assessee under sub-section (1) falls short of the aggregate of the tax, interest and fee as payable under the said sub-section, the amount so paid shall first be adjusted towards the fee payable and thereafter towards the interest payable and the balance, if any, shall be adjusted towards the tax payable.

(4) For the purposes of sub-section (1), interest payable under section 423 shall be computed on the tax on the total income as declared in the return as reduced by the amount of,— (a) advance tax, if any, paid; (b) any tax deducted or collected at source; (c) any relief of tax claimed under section 157; (d) any relief of tax or deduction of tax claimed under section 159(1) or 160 on account of tax paid in a country outside India; (e) any relief of tax claimed under section 159(2) on account of tax paid in any specified territory outside India referred to in that section; and (f) any tax credit claimed to be set off as per the provisions of section 206(2) (e) to (h) and 206(3) and (4).

(5) For the purposes of sub-section (1), interest payable under section 424 shall be computed on an amount equal to the assessed tax or, as the case may be, on the amount by which the advance tax paid falls short of the assessed tax.

(6) In sub-section (5), “assessed tax” means the tax on the total income as declared in the return as reduced by the amount of,— (a) tax deducted or collected at source, as per the provisions of Chapter XIX-B, on any income which is subject to such deduction or collection and which is taken into account in computing such total income; (b) any relief of tax claimed under section 157; (c) any relief of tax or deduction of tax claimed under section 159(1) or section 160 on account of tax paid in a country outside India; (d) any relief of tax claimed under section 159(2) on account of tax paid in any specified territory outside India referred to in that section; and (e) any tax credit claimed to be set off as per the provisions of section 206(2) (e) to (h) and 206(3) and (4).

(7) After a regular assessment under section 270 or 271 or an assessment under section 294 has been made, any amount paid under sub-section (1) shall be deemed to have been paid towards such regular assessment or assessment.

(8) If any assessee fails to pay the whole or any part of such tax, interest or fee as per the provisions of sub-section (1), he shall be deemed to be an assessee in default in respect of the tax, interest or fee remaining unpaid and all the provisions of this Act shall apply accordingly.

(9) The provisions of sub-section (8) shall apply without prejudice to any other consequences which the assessee may incur.

Introduction

Section 266 requires a filer to compute and pay self-assessment tax after accounting for advance tax, TDS/TCS and other permissible credits.

The return and payment records should reconcile so that the tax, interest and fee position is supported.

Key takeaways

1

Pay before furnishing return

The assessee pays net self-assessment tax, interest and fee before filing the required return, after accounting for available tax credits.

2

Short payments have an order

A partial payment is adjusted first against fee, then interest and then tax as the section directs.

3

Payment credits later assessment

Self-assessment tax is treated as paid toward a later regular or block assessment.

Obligation to pay tax before filing

Where tax is payable on the basis of a return required under Section 263, 268, 280 or 294 (after accounting for the credits listed below), the assessee must pay that tax together with any interest and fee payable for delay in filing the return or for default/delay in advance tax payment, before furnishing the return. The return must be accompanied by proof of payment of the tax, interest and fee.

Credits accounted for before computing what's payable

Before working out the self-assessment tax due, the following amounts already available to the assessee are taken into account:

  • Tax already paid under any provision of the Act
  • Tax deducted or collected at source
  • Relief of tax claimed under Section 157
  • Relief of tax or deduction of tax claimed under Section 159(1) or 160 for tax paid in a country outside India
  • Relief of tax claimed under Section 159(2) for tax paid in a specified territory outside India
  • Tax credit claimed to be set off as per Section 206(2)(e) to (h) and 206(3) and (4)
  • Any tax or interest payable according to Section 391(2)

Order of adjustment for a shortfall

If the amount paid by the assessee falls short of the aggregate tax, interest and fee payable, the amount paid is first adjusted toward the fee payable, then toward the interest payable, and the balance (if any) toward the tax payable.

How interest is computed

Interest payable under Section 423 (for delay in furnishing the return) is computed on the tax on total income declared in the return, reduced by advance tax paid, TDS/TCS, and the various reliefs/tax credits listed above.

Interest payable under Section 424 is computed on the "assessed tax" - or on the shortfall between advance tax paid and the assessed tax. "Assessed tax" here means tax on the total income declared in the return, reduced by TDS/TCS under Chapter XIX-B, the Section 157/159/160 reliefs, and the Section 206 tax credit.

Effect on regular assessment and default

After a regular assessment under Section 270 or 271, or an assessment under Section 294, any amount paid under this section is deemed to have been paid toward that assessment.

If an assessee fails to pay the whole or part of the tax, interest or fee due under this section, they are deemed to be an assessee in default for the unpaid amount, and all provisions of the Act apply accordingly - without prejudice to any other consequences the assessee may face.

Step-by-step flow for paying self-assessment tax under Section 266

  1. 1

    Is a return being furnished under section 263, 268, 280 or 294?

    Section 266(1) applies to tax payable on the basis of a return required under any of these sections.

    • No: Section 266 does not apply to the payment.
    • Yes: Go to the next step.
  2. 2

    Is any tax still payable after the credits in Section 266(2)?

    Deduct tax already paid, tax deducted or collected at source, reliefs claimed under sections 157, 159(1), 159(2) and 160, tax credits under section 206(2)(e) to (h), (3) and (4), and tax or interest payable under section 391(2).

    • No: No self-assessment tax arises under Section 266(1).
    • Yes: Go to the next step.
  3. 3

    Add interest and fee for delay in the return or default in advance tax

    Interest under section 423 is computed on the tax on declared income less the items in Section 266(4). Interest under section 424 is computed on "assessed tax" as defined in Section 266(6), or on the shortfall of advance tax against it (Section 266(5)). Section 266 does not state the rates; those come from sections 423 and 424.

  4. 4

    Pay before furnishing the return and attach proof of payment

    Section 266(1)(a) and (b) require payment of tax, interest and fee before the return is furnished, and the return must be accompanied by proof of payment.

  5. 5

    Was the full amount paid?

    If the payment falls short, Section 266(3) applies it first to the fee, then to interest, and only the balance to tax.

    • Yes: After a regular assessment under section 270 or 271, or an assessment under section 294, the amount is deemed paid towards that assessment (Section 266(7)).
    • No: The assessee is deemed to be an assessee in default for the unpaid amount (Section 266(8)), without prejudice to other consequences (Section 266(9)).

Practical checklist

Do

  • Reconcile tax payable with advance-tax payments and TDS/TCS credits before filing.
  • Pay any remaining self-assessment amount and retain the challan reference.

Avoid

  • Treat a TDS entry in the return as proof of credit without reconciling it to the available tax record.

Illustrative example

Worked example: a part payment and the order of adjustment

Hypothetical facts (illustration only, not a real taxpayer): Mr. Rao is preparing his return under section 263. The tax on the total income declared in the return is ₹3,40,000. Tax deducted at source is ₹2,10,000 and he paid advance tax of ₹50,000. Interest for advance-tax default works out to ₹6,000 and a fee of ₹5,000 is payable for delay in the return. All figures are assumed for illustration. He pays only ₹60,000 before filing.

  1. Tax payable after credits

    ₹3,40,000 − ₹2,10,000 − ₹50,000 = ₹80,000 (Section 266(2)(a) and (b)).

  2. Total due before filing

    Tax ₹80,000 + interest ₹6,000 + fee ₹5,000 = ₹91,000 (Section 266(1)(a)).

  3. Order of adjustment

    Under Section 266(3), the ₹60,000 goes first to the fee (₹5,000), then to interest (₹6,000), and the balance of ₹49,000 to tax.

  4. Unpaid amount

    Tax unpaid = ₹80,000 − ₹49,000 = ₹31,000. This matches ₹91,000 − ₹60,000 = ₹31,000. For this amount he is deemed an assessee in default under Section 266(8).

Outcome

  • Paying the full ₹91,000 before filing, and attaching proof, would have met Section 266(1).
  • A part payment does not reduce tax first; the fee and interest are cleared before any tax.

Frequently asked questions

Do I need to pay tax before I file my return?

Yes - Section 266 requires that if tax is still payable after accounting for TDS/TCS, advance tax and other reliefs already claimed, you must pay it (with applicable interest and fee) before furnishing the return, and attach proof of payment.

What happens if I underpay my self-assessment tax?

If you fail to pay the whole or part of the tax, interest or fee due under Section 266, you are deemed to be an "assessee in default" for the unpaid amount, and the Act's default-recovery provisions apply.

If I pay only part of what's due, what gets paid off first?

The amount paid is adjusted first toward the fee payable, then toward interest, and only the balance is treated as tax paid.

Need help applying this provision to your situation?

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Last updated 10 October 2026