When you do not file your Income Tax Return (ITR) on time, the government charges interest. This is covered under Section 423 of the Income Tax Act, 2025.
This interest is not a penalty, but a cost for delaying your tax responsibility. If you understand how it works, you can easily avoid paying extra money.
Section 423 explains that if you delay filing your income tax return or do not file it at all, you must pay simple interest at 1% per month.
This interest is calculated on the tax amount that is still unpaid. Even if the delay is small, interest will still apply. The law treats delay very strictly.
How Section 423 interest is calculated
The section gives a simple formula:
Interest = 1% × Tax Amount × Time (in months)
Here’s what each part means:
- Interest (I): Extra money you pay for delay
- Tax Amount (A): The unpaid tax on which interest is charged
- Time (T): Number of months of delay
Note: Even a part of a month is counted as a full month. So a delay of just a few days still becomes one month.
When Section 423 Interest Applies
This section covers different situations where delay can happen. The most common ones are:
- When you file your return after the due date, Interest starts from the due date and runs till you actually file.
- When you do not file your return at all, Interest runs till the date of assessment.
- When a return is filed after a notice from the department, Interest is still counted from the original due date, not from the notice date.
So in all cases, the law focuses on when the return should have been filed originally.
Interest Applicability on Late or Non-Filing of Income Tax Return
| Situation | Interest Period |
|---|---|
| Return filed after due date | From original due date → till actual filing date |
| Return not filed at all | From original due date → till date of assessment |
| Return filed after notice from department | From original due date (not notice date) → till actual filing date |
How the Time Period is Counted
The time for interest calculation starts from the due date of filing the return And ends on:
- The actual filing date, or
- The date of assessment, if return is not filed
This means the clock starts ticking immediately after the due date of income tax return filing passes.
On Which Tax Amount Interest is Charged
Interest is not charged on your full tax liability. It is charged only on the remaining unpaid tax. This unpaid tax is calculated after reducing certain payments.
Section 423 allows these adjustments:
- Advance tax paid: Any tax you already paid during the year reduces your liability.
- TDS or TCS: Tax already deducted or collected also reduces the amount.
- Tax reliefs (if applicable): Relief under sections like foreign tax credit can reduce tax.
- Tax credits set off: Any allowed tax credit also reduces the final amount.
After all these adjustments, the remaining balance becomes the base for interest.
The section also explains what happens if your tax changes later.
If your tax is increased after reassessment or recomputation, then the interest will also increase accordingly. If your tax is reduced, then any extra interest paid will be refunded to you. So the interest always follows the final tax amount.
There are a few important details people usually miss:
- Interest under this section is simple interest, not compound. So it is calculated only on the original unpaid amount.
- Additional income-tax (if applicable) is not included in the base amount
- Interest already paid earlier will be adjusted when recalculating
These small details affect the final amount, especially in reassessment cases.
Example
Let’s understand with a simple example.
Suppose:
- Total tax payable = ₹40,000
- TDS already deducted = ₹25,000
- Remaining tax = ₹15,000
- Due date = 31 July
- You file return on = 20 September
- Now count the delay:
- August → 1 month
- September → counts as full month
- Total delay = 2 months
- Interest = 1% × ₹15,000 × 2 = ₹300
- So, ₹300 is the extra cost (interest under section 423) for late filing.
This section is mainly about discipline. The government expects you to file your return on time. Even though 1% per month looks small, it can add up if:
- Your unpaid tax is high
- Your delay is long
So this is not just a technical rule. It directly affects how much money you pay.
Conclusion
Section 423 clearly says that delay in filing your income tax return will cost you extra money in the form of interest. It is calculated simply, but applied strictly from the due date of filing income tax return until filing or assessment.
The best way to avoid this is straightforward— file your income tax return on time and ensure your tax is fully paid before the due date.
