Only three days are left to file income tax returns (ITR) for assessment year 2018-19 (financial year 2017-18). It is compulsory for individuals who earn a specified amount of annual income to file ITR within a pre-determined due date. Filing the income tax return after the due date, which is August 31, 2018, will invite penalties from the income tax department, amount ranging from Rs. 5,000 to Rs. 10,000 depending on the degree of delay, according to the department's website - incometaxindia.gov.in. However, the due date for filing income tax return (ITR) for assessees in Kerala has been extended to September 15 on account of devastating floods.

Here are 5 things you need to know about income tax returns (ITR) filing:

1. Income tax is levied on individual taxpayers on the basis of a slab system. Different tax rates have been prescribed for different slabs. There are three categories of individual taxpayers- individuals (below the age of 60 years) which includes residents as well as non-residents, senior citizens (60 years and above but below 80 years of age) and super senior citizens (above 80 years of age). In the general category, individual with annual income up to Rs. 2.5 lakh is exempted from paying income tax. For senior citizens, individual with income up to Rs. 3 lakh is exempt from tax. For super senior citizens, aged 80 years and above, income up to Rs. 5 lakh is exempt from tax.

2. The Income Tax Department has provided online facilities - through its e-filing portal incometaxindiaefiling.gov.in - for individuals to file their ITR or income tax return for assessment year 2018-19.

3. However, filing or submitting the income tax return online does not complete the ITR process. The Income Tax Department has also mandated the public to verify the income tax return after submitting it. The taxman offers several ways such as mail, net banking, ATM and Aadhaar - to verify an ITR once it is submitted.

4. The Income Tax Department has provided seven forms - known as ITR forms - to enable assessees to file their income tax return online. These forms are called ITR 1, ITR 2, ITR 3, ITR 4, ITR 5, ITR 6 and ITR 7.

5. Taxpayers can make changes to an ITR, once filed till March 2019 (for financial year 2017-18, and assessment year 2018-19) in case an individual makes a mistake and wishes to make a correction, according to the department's website.