What Section 89 does, and that an NRI can claim it
Getting years of arrears in a single year is a rough deal, because Indian tax is charged at slab rates, so a lump that would have sat in lower slabs across several years instead gets taxed at your top rate all at once. Section 89 exists to undo exactly that. It re-computes your tax as if each slice of the arrears had been taxed in the year it actually related to, works out the difference against taxing it all in the year of receipt, and gives you that difference back as relief. It applies to salary and pension arrears or advance, arrears of family pension, and certain lump sums.
The correction worth making loudly: many websites say this relief is only for residents. It is not. The section gives the relief to any assessee, with no residence condition, so as an NRI you can claim it just as a resident can. It also survives the new tax regime, because Section 89 is a relief against your tax, not one of the deductions or exemptions the new regime strips away, so you get it whichever regime you are on. Under the Income-tax Act, 2025 the relief is renumbered to Section 157 from FY 2026-27, but for the year you are filing under the old law it is still Section 89.
The Form 10E step you cannot skip
There is one procedural trap that catches people, and it is unforgiving. To claim Section 89 relief you must file Form 10E on the tax portal, and it has to be filed before you file your return. This is not written into Section 89 itself as a penalty, it comes from the rules and a standing instruction that made online Form 10E compulsory, but the effect is very real: if you claim the relief without filing Form 10E first, the processing centre disallows it outright in the intimation and you lose it. So the order matters, Form 10E first, then the return claiming the relief.
One limit to keep in mind. If part of your lump sum was a voluntary-retirement payout on which you already claimed the separate voluntary-retirement exemption under Section 10(10C), you cannot also claim Section 89 relief on that same part, the law bars the double benefit. Beyond that, the arrears are taxed in the year you receive them, and Section 89 simply softens the rate. A practising CA computes the relief correctly across the relatable years, files Form 10E before the return, and makes sure the relief is not lost to a sequencing mistake.