Indian currency (भारतीय रुपया) is not only used by India as a legal tender.

Following countries also use it as legal tender:

  1. Nepal – The Nepalese Rupee is pegged at ₹0.625; the Indian rupee is accepted in Nepal, except ₹500 and ₹1000 banknotes, which are not legal tender in Nepal and is banned by the Government of Nepal, though accepted by many retailers.
  2. Bhutan – The Bhutanese ngultrum is pegged at par with the Indian rupee; both currencies are accepted in Bhutan.
  3. Zimbabwe – On 29 January 2014, Zimbabwe added the Indian rupee as a legal tender to be used.

source: Wikipedia