The unit of Bhutan currency is the ngultrum (Nu), which is pegged to the Indian rupee. The ngultrum is further divided into 100 chetrum. There are coins to the value of 25 and 50 chetrum and Nu 1, and notes of Nu 1, 5, 10, 20, 50, 100, 500 and 1000. The Nu 1 coin depicts the eight auspicious symbols called Tashi Tagye, while each note depicts a different dzong.
Indian rupees may be used freely anywhere in Bhutan (don't be surprised if you get change in rupees). Officially 500 and 1000 Indian rupee notes are not accepted due to large amounts of counterfeit notes; however, in practice 500s are usually accepted. Ngultrums cannot be used in India.
Bank of Bhutan (BoB), Bhutan National Bank and Druk PNB Bank ATMs accept some foreign credit cards, but ATMs in Bhutan use the magnetic strip rather than digital chips, and some foreign banks do not permit withdrawals via this method. The government also periodically blocks international ATM transactions for short periods to combat fraud. It always pays to carry cash in case you have problems.
Handicrafts, including Bhutan's celebrated textiles, extraordinary masks and Buddhist paraphernalia, are on most visitors' shopping lists. Traditionally haggling was not as common here as in Nepal or India, but these days you'll notice the price will drop remarkably as soon as you lose interest in a purchase. Overall the quality is good and vendors are happy to let you browse without the hard sell so common in neighboring countries.