NRI status immediately after commpleting 182 days or FY wise ?

As per Income tax act you remain NRI for complete financial year, if you remain less then 182 days in India, in that year. (that being one of the conditions as per the act)

Check that you remain maximum 181 days in India including days of arrival & departure, to qualify for NRI status IN THAT FINANCIAL YEAR. 

Thanks than in my case by what date I need to change status of my saving bank account / Demat / Trading account to NRI ?

If you have stayed less then 182 in India in FY 2024-25, you will be NRI for  FY 2024-25. For FY 2025-26 & onwards, we need to check your stay in India for that particular year along with your total stay outside India for earlier years. Most probably would become RNOR for that year if you are returning to India after many years of stay outside the country.

Refer: https://cleartax.in/s/income-tax-act-residential-status

NRI status is always determined on a financial year basis, not on the day you complete 182 days.

At the end of each financial year (April 1 to March 31), you count the number of days you stayed in India during that year. If you stayed for 182 days or more during the financial year, you are Resident for that year. If fewer than 182 days, you are NRI for that year.

There is no mid-year switch. Completing 182 days outside India on, say, November 15 does not make you an NRI from November 15. Your residential status for the entire FY is determined at year-end based on total days of stay.

For people close to the threshold, also check the secondary test:
- If you stayed 60 days or more in this FY AND 365 or more days in the preceding 4 FYs combined, you are Resident even if you stayed for less than 182 days this year. This rule has an exception for Indian citizens who went abroad for employment or as crew members.

After returning to India after many years abroad, you may qualify for RNOR (Resident but Not Ordinarily Resident) status for up to 3 years, which exempts your foreign income from Indian tax.

This [RNOR status and income tax guide for 2026](https://taxgarden.in/blog/rnor-resident-not-ordinarily-resident-income-tax-india-2026) explains the exact tests and which income is taxable at each stage of returning to India.