I collect documents of :
Form 16 if taxes are deducted on salaries, or if my income from salary is over taxable limits. This is collected from my employer.
If I am a pensioner, I will get a Form 16 from my bank if taxes are deducted, and should ask for a pension certificate, which my banker will oblige. I can even total up the pension received from my bank statement or passbook, but its better to obtain a pension certificate.
If no taxes are deducted and I am in private or government employment, and I am below taxable limit, I can request for a salary certificate from my employer.
I should fill out my salary under various heads per the form as shown in the salary certificate/Form 16 which will be matching with the computation I made out. This lists down Salaries, Allowances, Perquisites, Deductions (Being standard deduction and others).
I arrive at my net income from salaries