Basic things require to file your return

Basic things require to file your return
1.Form 16
The Form 16 is an important document for people who do a job and earn a salary income. This document is a certificate that you get from your employer. Look at it as a proof of employment and remuneration received. The Form 16 certifies that you have received salary from your employer for a particular period and your employer has deducted TDS–tax deducted at source–on the salary paid to you.

Salaried employees receive the Form 16 once a year, after a particular financial year has ended. If you changed jobs in the financial year, you would receive a Form 16 from each employer in the months of May or June.
The fuss about the Form 16
Typically, a couple of months prior to the deadline to 
file income tax returns, you will hear a lot about the Form 16. This is because it is one of the most important tax forms and contains most of the information you would need to prepare and file your tax returns.
On Filingmantra, you have to just upload your Form 16. We’ll automatically prepare your tax returns for you.
Part A and Part B
Your Form 16 has two parts. Part A has all the basic details about your employer and you and your employment period with the employer. Part B is critical because it has a detailed breakup of your salary and the tax-saving deductions that you have claimed by way of certain investments and expenses.
It is an employer’s responsibility to provide the Form 16 when there is tax deducted at source. If you haven’t received your Form 16, you should ask your employer for it. This is one document that cannot be downloaded online.
E-filing using Form 16
On the Income Tax Department’s website, you can e-file your tax returns using the information provided in your Form 16. The information will have to be manually entered into the relevant fields and then submitted to get your returns filed.
You have to just 
upload your Form 16 and the website will automatically prepare the returns for you. 
The other Form 16
There’s also something like the Form 16A. While the Form 16 has details about your salary, Form 16A has details of tax deducted at source on other incomes. These other sources of incomes can be fixed deposits with banks, insurance commissions, house properties, etc. The Form 16A is provided by the tax deductor and there will be as many Form 16As as there are deductors for you. For example, if you have fixed deposits with two different banks and TDS is deducted by both, the two banks will issue separate Form 16As to you.
This is why the Form 16 is an integral document to be able to 
file your tax returns. You should file your returns even if your employer doesn’t issue a Form 16 after deducting TDS. This is the employer’s mistake and they will face penalties for the same. It is your responsibility to file your tax returns when you earn income that is above the taxable limit and the Form 16 can help you do that with ease.

2. Which form to fill 
If you using the online platforms, this is an automated process. "The correct ITR form gets selected automatically on the basis of the information provided by the taxpayer,"  However, if you are using the government site, you need to know which form is for you. Each form has it's limitations. For one, you may have income from salary only but you can't file ITR 1 if you own more than one house or have gained  from trading in shares. If you own more than one house and do not have capital gains or foreign income or assets, you can file ITR 2A. Similarly, ITR 4S is a much simpler form to fill compared to the bulky 20-page-long ITR 4, if you have income from a business or are a freelancer. If you choose ITR 4S, there is no need to maintain books, profit &loss statements or audits. You don't have to pay advance tax either. However, your business's gross receipts or turnover of the business should not be more than Rs 1 crore and it should not be registered as a company. Your tax liability would be calculated on the basis of a 'presumed business income', irrespective of what your actual income may be. Section 44AD of the Income-Tax Act says under the presumptive method, the net income is estimated to be 8% of gross receipts for businesses. This year onwards, even freelancers earning less than Rs 50 lakh per annum can also file ITR 4S. "A new section has been inserted in the I-T Act Section 44ADA under which professionals with receipts of Rs 50 lakh or less could opt for the presumptive scheme. Their income shall be assumed to be 50% of their receipts,".

3. TDS and Form 26AS 
You need to cross-check your TDS deductions with the figures reflected in Form 26AS, especially if you have interest income from bank deposits or any other sources. Form 26AS also records interest income in cases where Form 15 G/H is submitted by the taxpayer. So, in case you have erroneously submit these forms where there was a tax liability, you should make corrections. "The taxpayer should add this interest income to the list of 'income from other sources' and compute the tax liability calculated as per tax slab rate," says Sankla. Form 26AS can be downloaded from the TRACES site. The tax department's e-filing site also provides a link. However, be careful while selecting the Assesment Year (AY). "Taxpayers get confused between Assessment Year (AY) and Financial Year (FY) and they end up filling up wrong year's data in the return form. This may result in a huge tax demand due to tax credit mismatch," . 

4. Declaring 'Income from Other Sources' , capital gains 
Once you have figured out Form 16, it is merely copying figures from it on the ITR Form. But if you have income from other sources you need to be careful. Lately, the sleuths have become vigilant and you may end up with a notice. 
Typical incomes under this head include interest on bank or other deposits, taxable dividends, income from securities by way of interest, pension received by the legal heirs of an employee, income from subletting, winnings from lotteries, races and gambling. 
Do not miss out reporting income from a second house. Even if it is not rented out, you have to pay a tax on the basis on 'deemed income'. Good thing is that if you have incurred any specific expenses for earning any of the above income then you can claim deduction for the same too. Capital gains or losses is another section where taxpayers tend to make mistakes. Capital gains/losses have to be reported in Schedule CG of form ITR 2. 

5. How to e-verify 
You may have filed your returns on time but the tax-filing process is incomplete if ITR-V doesn't reach the department within the stipulated time. You won't get your refunds and worse, your returns filing won't be considered valid if the department doesn't receive a signed or verified copy of ITR V within 120 days of filing the returns. Apart from mailing the ITR V to the CPC in Bengaluru, you can now e-verify by linking your Aadhaar or through netbanking. For Aadhaar-linked verification, you have to be registered on e-filing site and provide your Aadhaar number. Once the validation is done, you will receive an OTP (which will be your electronic verification code) on your Aadhaar registered mobile number, which will be valid for the next 10 minutes. Submit this to e-verify your ITR V. In case your PAN and Aadhaar details don't match or you are still not registered under UIDAI, verify using your netbanking account.