Tax planning is the most important part for any investor as it reduces the profits which one has earned and hence most investor worry the most.
With respect to NRI's its becomes even more important has they have to deal with taxation norms of 2 countries ie. INDIA as well as country where they reside.
Though India has signed DOUBLE TAXATION Avoidance Treaty (DTAA) with most of the countries still NRI's worry that they would not have to pay double taxes.
Generally every indian has to pay tax on various income earned within indian territory and same is true for NRI's also . Income can be anyone of the below (Some example given) and they have to pay tax