
How to File Rectification Under Section 154(1)
Once you have filed an income tax return, the income tax department processes the return and issues an intimation. This intimation provides information about the return you submitted and the figures recorded by the department.
If a discrepancy arises, such as a demand for additional tax or a higher refund than what you initially claimed, you can take the following steps:
1) File a Rectification Request:
2) Agree with the Demand and Pay the Tax:

What errors can be corrected by filing a rectification?
A rectification request under section 154(1) is permitted by the income tax department to address mistakes when there is an evident error in your Income Tax Return. The following types of errors can be rectified by filing a rectification request:
1) An error of Fact.
2) Arithmetic Mistake.
3) Small Clerical Error.
4) Error Due to Overlooking Compulsory Provisions of Law.

Please note that you can submit a rectified JSON only for activities mentioned below:
1) To correct email ID or mobile number or address.
2) Correct the TAN or assessment year, challan number or BSR code in ‘Schedule TDS’ or ‘Taxes Paid’.
3) To correct the bank account number or IFS code in bank details.
4) Correct any other detail in the return that does not result in a change in the gross total income or total income or result in an excess refund claim when compared with the return already submitted.
You cannot submit a rectification return for the following activities:1) To report Chapter VI deductions which were left out in the return already filed.
2) To claim loss in the rectification return which was missed out in the already filed return.
3) You cannot claim additional TDS credit or claim a missed out tax payment challan and claim the tax credit/refund.

To file a rectification return, there are two scenarios in Software:
1) In the case of filing rectification after submitting the original return.
2) And filing rectification after submitting the original return and revised return.

1: In the case of filing rectification after submitting the original return:

Step 1:
Go to Transaction >> Filing Information:

Step 2:
Click on Filing Status >> Select Revised return >> And fill in the details of the original ITR (Income Tax Return) that was filed and then Click on "Save" Button:

Step 3:
Generate Computation and then Generate the JSON/XML file then Upload on Income tax Portal:

2: Filing rectification after submitting the original return and revised return.

Step 1:
Go to Transaction >> Filing Information:

Step 2:
Click on Filing Status >> Select Revised return >> And fill in the details of the original ITR (Income Tax Return) that was filed:

Step 3:
Generate Computation and then Generate the JSON/XML file then Upload on Income tax Portal:

Remember, when uploading rectification after filing the original return and revised return, select the 'Revised' option in the software. Then, upload the JSON/XML file under the Rectification Head on the Income Tax Portal.

A rectification request can only be made for returns that have been processed at the CPC, Bangalore. If, while correcting a 'mistake,' there's a change in income, filing a rectification is not suitable. Additionally, no new deductions or exemptions are allowed to be claimed in such cases. If there's a need to adjust the reported income, it's recommended to file a Revised Income Tax Return instead.
Hope This Helps.