The new regime is the default now. When the old one still wins.

For most salaried Indians the tax decision used to be an active one. You picked the old regime, you gathered your rent receipts and 80C proofs, and you filed. That default has now flipped. Unless you tell your employer otherwise, your salary is taxed under the new regime, and the burden is on you to opt out if the old one serves you better.

Default is not the same as best

The new regime is simpler by design. It offers wider slabs and a standard deduction, but it strips away almost every exemption that made the old regime worth the paperwork: house rent allowance, the section 80C basket, the 80D health-insurance deduction, the interest on a self-occupied home loan. For a large number of salaried people, especially those early in their careers or without a home loan, that trade is a good one. The lower slab rates simply beat the deductions they would have claimed anyway.

But default is a policy choice, not a personal one. The system picks the option that is right on average, and you are not an average. If your deductions are large, mostly because you pay meaningful rent, service a home loan, and fill your 80C every year, the old regime can still leave more money in your account. The only way to know is to compute both, on your actual numbers, and compare the tax at the bottom.

Run the arithmetic on both

The comparison turns on a single question: how much can you legitimately deduct? Under the old regime, every rupee of deduction lowers your taxable income; under the new regime, most of those deductions simply do not exist. So the new regime starts ahead on rates and the old regime claws back ground with every deduction you can prove. The levers that matter most for a salaried filer are:

• House rent allowance, if you actually pay rent and your salary structure includes an HRA component.
• Section 80C, up to Rs 1,50,000 across EPF, PPF, ELSS, life-insurance premiums, home-loan principal and children's tuition.
• Section 80D, for health-insurance premiums covering you and your parents.
• Section 24(b), the interest on a home loan for a self-occupied property, up to Rs 2,00,000 a year.
• The additional NPS deduction under 80CCD(1B), worth up to Rs 50,000 on top of your 80C limit.

Add those up honestly. For someone renting in a metro with a home loan and a fully funded 80C, the total can cross several lakh rupees, and at that level the old regime often wins. For someone with none of those, the total is small, and the new regime's wider slabs win comfortably. Everyone else sits somewhere in between, near a break-even line.

Where the old regime still wins

There is a deduction figure at which the two regimes produce exactly the same tax. Below it, the new regime is cheaper; above it, the old one is. That break-even shifts with your income, because the slab rates and the standard deduction interact differently at each level, but the logic never changes: the old regime only pays off once your provable deductions are large enough to outweigh the new regime's lower rates.

This is why a generic answer is worthless. Two colleagues on an identical CTC can land on opposite regimes purely because one rents and repays a home loan while the other lives in a family house and invests nothing beyond EPF. The regime is not a feature of your salary; it is a feature of your whole financial life.

The right regime is not the one your neighbour picked or the one your payroll defaults to. It is the one that is cheaper once you have added up every deduction you can actually prove.

What to actually do

Treat the choice as an annual review, not a one-time decision. Your deductions move: a new home loan, a change of city, a parent to insure, a year you could not fund your 80C. Any of those can push you across the break-even line. Salaried employees can switch between regimes each year at the time of filing, so a wrong call in April is not permanent, though it does affect the tax deducted from your monthly salary in the meantime.

• Total your realistic deductions for the year, not the ones you hope to make.
• Compute the tax under both regimes on that total, or let a tool do it to the rupee.
• Declare the cheaper regime to payroll early, so your monthly take-home is not over-taxed all year.
• Re-check next April, because the numbers that decided it can change.

The new regime being the default is a convenience, not a verdict. Spend twenty minutes on the arithmetic once a year and you turn a silent policy setting back into a decision you actually made.