ITR Filing: In case the assessee has filed his Income Tax return (ITR) with errors then the person is granted an opportunity to file a revised ITR in view of the provisions of section 139(5) of the Income Tax Act, 1961, within the prescribed time limit, i.e. 1 year from the end of the relevant assessment year.  For example, if ITR for AY 2018-19 is wrongly filed, then the error/ omission in the original ITR filed can be rectified by filing a revised ITR on or before 31 March 2019. 

What are the common mistakes while filing an ITR?
Filing an ITR is a gruelling process and prepare it at the last minute may result in mistakes that might have a negative impact on your finances, says Taranpreet, TASS Advisors Partner. Here is a list of some common mistakes people make while filing ITR:
1. Incorrect personal details
2. Choosing the wrong ITR form
3. Mistakes in claiming deduction under section 80C of the Income Tax Act, 1961
4. Non-reconciling TDS with Form 26AS
5. Non-reporting exempt incomes
6. Quoting wrong assessment year
7. Not setting off losses from the previous year
8. Failure to pay self-assessment tax prior to the filing of return
The rate of penalty:
Under section 270A, under-reporting of income can attract a penalty of up to 50% of the tax payable on under-reported income. On the other hand, in case of misreporting, the penalty can be as high as 200% of the tax payable on the misreported income. 
For instance, if you are in 30% tax bracket and under-report an income of Rs. 1 lakh in your returns, upon assessment, the assessing officer can impose a penalty of up to about Rs. 15,000 (50% of the tax on under-reported income, i.e., Rs. 30,000). If the misreported income is Rs. 1 lakh, the penalty can be up to 200% of the tax on unreported income.