What is Form 12B?
Form 12B solves a problem created by the way salary TDS works. Under section 392 of the Income-tax Act, 2025, and section 192 of the 1961 Act before it, an employer deducts tax on its estimate of the employee's annual income, and a new employer joining someone in, say, October knows only what it will pay from October onward.
So it estimates on six months of salary. Meanwhile the previous employer estimated on the months it paid. Each computed a smaller annual income than the employee actually has, and each therefore deducted less tax than the combined position requires.
The employee closes that gap by furnishing Form 12B to the new employer, setting out what the previous employer paid and deducted. The new employer then computes tax for the year as a whole, taking credit for the tax already deducted, and deducts the balance over the months left.
Note that the direction of travel is from employee to employer. The previous employer does not send it. The employee obtains their own salary and TDS details, usually from payslips or the previous employer's certificate, and hands the statement to the new one.
Why does skipping it produce a tax bill?
The under-deduction is arithmetic rather than an error, and it comes from the same reliefs being granted twice.
Both employers allow the standard deduction from salary. Both start the employee at the bottom of the slab table, so income that should have been taxed at a higher rate gets taxed at the lowest rates twice over. Both may allow the same Chapter VI-A deductions if the employee declared them in each place. And any rebate for total income below a threshold may be applied by both, when on combined income it may not be available at all.
Here is a worked example. An employee earns 6,00,000 rupees from April to September and 7,00,000 rupees from October to March. Each employer computes on its own figure, applies the standard deduction, and works up the slabs from the bottom. The true position is a single income of 13,00,000 rupees with one standard deduction and the higher slabs engaged. The difference between the two calculations is what the employee owes at filing, and it can run to a significant amount.
Furnishing Form 12B does not increase the tax due. It moves it into monthly deductions, where it is manageable, instead of leaving it as a lump sum plus interest for deferring advance tax.
What does Form 12B contain?
The statement covers the previous employment for the part of the financial year already elapsed.
| Field | Detail |
|---|---|
| Previous employer | Name, address and TAN |
| Period | Months of employment during the current financial year |
| Salary | Salary paid, less exemptions such as house rent allowance claimed there |
| Deductions allowed | Provident fund, professional tax and Chapter VI-A deductions given by the previous employer |
| Tax | Tax deducted at source and deposited |
Accuracy matters on the deductions column in particular. Chapter VI-A amounts already allowed by the previous employer should not be claimed again in full with the new one, since the statutory ceiling applies to the year rather than to each employment.
How is it different from Form 12BA and Form 12BB?
Three forms with almost the same number do quite different jobs, and they are regularly confused for one another.
| Form | Who prepares it | Purpose |
|---|---|---|
| Form 12B | Employee | Reports previous employer salary and TDS on joining mid-year |
| Form 12BA | Employer | Statement of perquisites and profits in lieu of salary, issued with Form 16 |
| Form 12BB | Employee | Declares investments, rent and deductions to the current employer |
A mid-year joiner typically deals with two of them. Form 12B goes in once, on joining, covering what came before. Form 12BB goes in for the year ahead, covering what they intend to claim.
What if it is not furnished?
Nothing stops at the time. The new employer is entitled to compute TDS on the salary it pays, and it is under no obligation to hunt for earlier income it has not been told about. Payroll runs normally and take-home looks healthy.
The consequence lands at filing. The employee reports both employments, the combined tax is computed once, credit is taken for what both employers deducted, and the balance is payable as self assessment tax before the return can be filed. Where the shortfall is large, interest for deferment of advance tax can apply on top.
The other visible effect is on the certificates. Two employers issue two Form 16s, each covering its own period, and neither reflects the year as a whole. Where Form 12B was furnished, the new employer's certificate accounts for the previous salary, which makes the return simpler to file and easier to reconcile against Form 26AS.
Statutory reference
- Act
- Income-tax Act, 2025, with the Income-tax Rules, 2026
- Section
- From tax year 2026-27: rule 204(1) of the Income-tax Rules, 2026 (Form 122, furnished by the assessee to the person responsible for paying salary under section 392(1)), with section 392 of the Income-tax Act, 2025 (deduction from salary). For tax year 2025-26 and earlier, preserved by section 536(2) of the Income-tax Act, 2025: section 192(2) of the Income-tax Act, 1961 and Rule 26A of the Income-tax Rules, 1962 (Form 12B).
- Key limits
- Section 536 is on its amended-section list, but section 122 of that Act touches only sub-section (2) clauses (g) and (h), on interest for refunds and defaults and on clawback of deductions. Rule 204(1) lists what may be furnished: salary due or received from any other employer in the tax year, loss under Income from house property, income under any other head that is not a loss, and tax deducted or collected under Chapter XIX-B in the same tax year. Note the wording: the rule says the assessee may furnish these particulars, so the initiative sits with the employee rather than being an obligation the employer can enforce. The references are historical and deliberate. Section 536(2) of the Income-tax Act, 2025 saves the repealed Act for tax years beginning before that date, so an employer dealing with tax year 2025-26 or earlier is still governed by it.
Frequently asked questions
What is Form 12B used for?
It reports your salary, deductions and tax deducted from a previous employer to a new employer when you join part way through a financial year, so the new employer computes TDS on your total income for the year rather than on its own portion.
Who issues Form 12B?
The employee furnishes it to the new employer. It is not issued by the previous employer, although the salary and TDS figures in it come from that employment's payslips or certificate.
Is Form 12B mandatory?
It is the prescribed route for reporting previous employer income, and furnishing it is how you avoid a shortfall. If you do not, the new employer deducts on its own salary alone and you settle the difference as self assessment tax at filing.
What is the difference between Form 12B and Form 12BB?
Form 12B looks backwards, reporting salary and TDS from a previous employer. Form 12BB looks forwards, declaring the investments, rent and deductions you intend to claim with the current employer for the year ahead.
I did not submit Form 12B. What happens now?
You combine both Form 16s when filing, compute tax on the total, take credit for all TDS deducted, and pay the balance as self assessment tax. Expect the balance to be sizeable, because both employers gave you the standard deduction and the lower slabs.
Does the new employer verify what is in Form 12B?
The employer relies on the statement furnished, which is why the figures should be taken from payslips or the previous employer's certificate rather than estimated. Wrong figures produce a deduction that will not reconcile against Form 26AS at year end.
How Engage helps with Form 12B
Engage prompts a mid-year joiner for previous employer salary and TDS as part of onboarding rather than leaving it to be discovered at year end, then folds those figures into the annual projection so the deduction reflects total income from the first payroll run. The certificate issued at year end accounts for the earlier employment.
See onboarding and payroll in Engage