Why a job switch leaves tax unpaid
Each employer works out tax as if it were your only employer for the year. Your old employer projected a full year at your old salary and deducted a twelfth of that tax each month. Your new employer does the same with its own salary, starting from scratch. Neither sees the whole picture unless you give it to them.
Two things go wrong as a result. The standard deduction and the lower slab bands are applied by each employer separately, so you effectively get them twice during the year. And if either salary alone falls under the ₹12 lakh rebate limit while the two together do not, both employers deduct nothing at all. The shortfall only appears when the two Form 16s are added together at filing.
The ₹12 lakh trap
This is the case that catches most people in 2026. Say you earned ₹1 lakh a month for six months, then moved to ₹1.4 lakh a month. Each employer sees income that would be under ₹12 lakh for a full year, so each applies the rebate and deducts nothing. Your actual income for the year is ₹14.4 lakh, which is well over the limit, and the tax due is ₹88,140. Every rupee of that is payable at filing, with interest if you leave it late.
How to avoid it
Give your new employer the details of your earlier salary and the tax already deducted. Under the Income-tax Act, 2025 this is done on Form 124, which replaced Form 12B. Your new employer then computes tax on your combined income and deducts the balance over the remaining months. The total you pay is the same, but it is spread through the year instead of landing in one sum.
If the switch has already happened and you did not declare, you can still pay the shortfall as advance tax before 15 March to avoid most of the interest. Use the figure above as a starting point and confirm it against both Form 16s when they arrive.
Three things worth checking
First, confirm the months. A notice period paid in lieu, or a joining date mid-month, changes the count and the tool assumes whole months.
Second, look for a gap between the two jobs. A month without salary reduces your income for the year, which can only reduce the tax due. The tool handles this if the two month counts add up to less than twelve.
Third, check for a final settlement from the old employer. Leave encashment, gratuity and a bonus paid at exit are taxed differently from regular salary and are not included here. Our salary arrears relief calculator covers arrears, and gratuity has its own exemption limits.
Common questions
Will the new employer refuse to take my old salary details?
No. Form 124 exists precisely for this, and payroll teams handle it routinely. Give them the figures from your old payslips or the relieving letter, including the tax deducted and the professional tax paid.
I declared, but the new employer still deducted too little. Why?
Some employers only take the declared income into account from the month you submitted the form, or do not include the old employer's tax deducted. Check the tax computation on your new payslip rather than assuming it is right.
Does switching mid-year change my regime choice?
You can choose either regime when filing, whatever you told each employer. If the two employers deducted under different regimes, the return still has to use one, and the shortfall or refund follows from that.
What if I had more than two employers?
The same logic applies, only with more Form 16s to add. The tool handles two. For three or more, add the earlier jobs together as the old salary and treat the latest as the new one, which gives a close estimate.
Does this not match your payslip, or has a rule changed? Tell us and we will check it. Answers are published on our questions page.
This calculator gives an estimate for guidance and assumes salary is your only income. Last updated 6 October 2026.