For some online tax filers, choosing the right form is not an issue. "A taxpayer has to just enter what he has earned under different heads of income and the portal automatically chooses the applicable form," says Sudhir Kaushik, co-founder and CFO of Taxspanner. com.

For instance, if the person has only income from salary and no exempt income, his return will be filed using ITR 1, but if he made some capital gains, has rental income from more than one house or his exempt income exceeds Rs 5,000, ITR 2 will be used.

However, taxpayers who upload their returns through the official Income Tax Department website will have to be more careful about the form they use. Delhi-based Kuldip Kaushik (see picture) used the ITR 1 last year, but since he had dividend income of over Rs 5,000 for the year 2012-13, he will have to use ITR 2 this year.

If a taxpayer uses the wrong form and the mistake is discovered by the tax authorities, the return may be rejected. Every year, thousands of defective returns are sent back to taxpayers. A defective return is not an earth shattering matter. If you get a notice, you will have to file a revised return within 15 days. If you meet the deadline, the return is treated as valid. Get delayed and your return will become invalid and you will have to file afresh.

"If you discover on your own that you have made a mistake in the return or used the incorrect form, you can file a revised return to rectify the mistake," says Agrawal. Your new return will overule the previous one if the assessment has not been completed.

Before you sit down to file your returns this year, spend a few minutes to check whether the tax you paid for last year has been correctly credited to your name. The Form 26AS has details of the tax deducted on behalf of the taxpayer and can be easily checked online. Noida-based Brijendra Singh wishes he had done so last year.