What you will require?
Every employer will give you Form 16 which will have details such as gross total income from salary, tax deducted at source and deductions under Section 80C. If you have informed your new employer about your previous salary, the Form 16 from your new employer will have the computed numbers. However, if you haven't informed your previous employment salary, you might have to pay the tax that you are liable for. You can also manually calculate the gross salary for filing your ITR.

How to file?
If you plan to e-file you returns on the income tax website all by yourself, you will have to first get all the Form 16s with you. Once you login, you will have to link your Aadhaar which happens within a few seconds if there is no discrepancy in your Aadhaar and PAN details. Once linked, you can start the e-fling process.

First, you have to pick the right ITR form and then provide general information such as address, full name and whether revised or original ITR. In the income details section, you need to enter income from salary. Here you will have to manually add the income from both the companies. Once added, you have to give your deduction details under 80C. Then the system will compute the tax payable.

Once computed, in the next page you will get details of tax deducted at source from salary. In case the new employer details is not mentioned, you have the option to add it. Once added, you can verify the taxes paid and also get details of refund or amount payable if any. You can reconcile the details of the taxes paid through Form 26AS which is available on the income tax website.

If you find the process cumbersome there are fintech websites such as cleartax.in and taxspanner.com, which allow you to do the process on their website by uploading all Form 16s. You don't have to manually calculate your income in this case.

Things To Remember
If you have not reported your old salary to your new employer, the new company many not factor in your old income and hence deduct lower tax.

Similarly, if you haven't informed your new employer about your 80C deductions done by your previous employer, you may end up getting deduction twice. In such a situation you will have to reconcile the details while filing returns.