Main categories of NRIs:
The following are the main three categories of NRIs:-
                         (i) Indian citizens who stay abroad for employment or for carrying on a business or Vocation or any other purpose in circumstances indicating an indefinite period of stay abroad.
                         (ii) Indian citizens working abroad on assignment with foreign government agencies like United Nations Organisation (UNO), including its affiliates, International Monetary Fund (IMF), World Bank etc.
                         (iii) Officials of Central and State Government and Public Sector undertaking deputed abroad on temporary assignments or posted to their offices, including Indian diplomat missions, abroad.

The residential status for the Income Tax Act is determined in section 6 as under:

1. An individual will be treated as a resident in India in any previous year if he fulfills any of the following two conditions:

(a) he/she is in India in that year for period or periods amounting in all to 182 days or more, or

(b) Having within the four years preceding that year been in India for a period or periods amounting in all to 365 days or more, and has been in India for 60 days or more in that year.

2. Under Explanation to section 6 (1) of the Income-tax Act, the residential status of an individual who is rendering service outside India and who visits India during leave or vacations in any previous year or an individual who is outside India and who comes on a visit to India in any previous year will be determined as under :

(a) An Indian citizen who leaves India in any previous year for the purpose of employment outside India or as a crew member of an Indian ship would be treated as a resident in India if he stays in India in that year for 182 days or more [instead of 60 days as stated in 1 (b) above ]. Conversely, if he stays in India for less than 182 days, he will be treated as non-resident for that year and his foreign income would not attract tax liability.

Further, w.e.f. 1st April, 1999, a crew member will be treated as non-resident in India if he is on board such ship outside the territorial water of India for 182 days or more during any year.

(b) An Indian citizen or a person of Indian origin who resides outside India and who comes on a visit to India in any previous year will be treated as resident in India if he stays in India in that year for 182 days or more [instead of 60 days as stated in 1 (b) above.]

Conversely, he will be treated as non-resident if he stays in India in that year for less than 182 days.

(3) An individual (whether Indian citizens or not) who is outside India and who comes on a visit to India in any previous year will be treated as "non-resident" in India if he stays in India in that previous year less than 182 days subject to the condition that during the preceding four previous years his stay in India does not amount to 365 days or more.

An Individual who fulfills any of the conditions mentioned in section 6(1) is treated as resident in India. But in order to become an "ordinarily resident", he must satisfy the following two conditions as laid down under section 6(6) (a) of the Income-tax Act, 1961:

(i) He should have been resident in India in nine out of the ten previous years preceding the previous year in which he is resident within the meaning of section 6(1); and

(ii) He should have been in India for a period or periods amounting in all to 730 days or more during the seven years preceding that previous year.

If he does not fulfill any of the above conditions, he will be treated as "not ordinarily resident".

(4) An individual who does not satisfy both the conditions as mentioned above as laid down in section 6 (1) will be treated as "non-resident" in that previous year.

(5) A Hindu undivided family, firm or other association of persons will be treated as "non –resident" in India in any previous year if the control and management of its affairs is situated wholly outside India during that year.

(6) A company will be treated as "non-resident" in India in any previous year if it is not an Indian company and also the control and management of its affairs is not situated wholly in India in that year.