As of July 2013, 17 of the 28 countries of the European Union have adopted the euro. The remaining 11 countries, including Great Britain, Denmark, and Sweden have retained their own currencies. The advantage of adopting the common currency is that each of the adopting countries has the same ___________________, making it easier to compare prices in different countries.

Unit of account, account currency or theoretical currency is a monetary unit of non-physical existence (that is, it is not minted) that, despite being imaginary (or, rather, thanks to it), is used in commercial transactions and accounting, and measures the market value.

Goods for sale in a market are adjusted using a unit of account. In this way the value is decided by the seller and expressed to the buyer. This occurs explicitly when it comes to a market that uses currency, but also implicitly when transactions are made through bartering.

Although the form of computing the official accounting can be determined by the economic authorities, the use of one or another unit of account can be carried out at the preference of the economic agent, provided that the cash payments are made in a means of payment accepted by both parties of the transaction, so that the correspondence of the currencies with the account units must be fixed or subject to quotation.