The Japanese currency is the yen(円, en). One yen corresponds to 100 sen. However, sen are usually not used in everyday life anymore, except in stock market prices. Bills come in 1000 yen, 2000 yen (very rare), 5000 yen and 10000 yen denominations. Coins come in 1 yen, 5 yen, 10 yen, 50 yen, 100 yen and 500 yen denominations. Counterfeit money is not an issue in Japan. Foreign credit cards are accepted mostly at major hotels and some stores in Tokyo, but most Japanese stores and lots of ATMs will not be able to run them. It is advised that cash is kept on your persons at all times.
Tipping is not customary in Japan, although fancy restaurants apply 10% service charges and 24-hour “family restaurants” such as Denny's and Jonathan's usually have a 10% late-night surcharge. If you want to show your gratitude to someone, give them a gift rather than a tip. If you do choose to give someone a cash gift, place the money in an envelope first.
Consumption tax in Japan is a flat 8% on all items. Stores are required to list the after-tax price, so what you see is what you should pay. Tax free shopping is available to foreign tourists only at a small number of licensed stores (typically major electronics and department stores in large cities) when making purchases of over 10000 yen at a given store on one calendar day. In case of consumable goods, such as foods, medicines and cosmetics, the consumption tax is waived for purchases of over 5000 yen, but the package of such goods must be kept unbroken until after departure from Japan. Note that at some shops, it is necessary to first pay the full price at the cashier and then obtain a refund at a customer service desk.