Denmark 100 Kroner, 2015, B936d, P66d, UNC. Banknotes of the euro, the common currency of the eurozone (euro area members), have been in circulation since the first series (also called ES1) was issued in 2002. The euro was established in 1999, but “for the first three years it was an invisible currency, used for accounting purposes only, e.g. in electronic payments”. In 2002, notes and coins began to circulate. The euro rapidly took over from the former national currencies and slowly expanded around the European Union.

The euro banknotes are pure cotton fibre, which improves their durability as well as giving the banknotes a distinctive feel. They have a variety of color schemes and measure from 120 by 62 millimetres (4.7 in × 2.4 in) to 160 by 82 millimetres (6.3 in × 3.2 in) (first series) and from 120 by 62 millimetres (4.7 in × 2.4 in) to 153 by 77 millimetres (6.0 in × 3.0 in) (second series).

The euro notes contain many complex security features such as watermarks, invisible ink characteristics, holograms, optically variable inks and microprinting that document their authenticity. While euro coins have a national side indicating the country of issue (although not necessarily of minting), euro notes lack this.

Order Undetected Counterfeit Denmark 100 Kroner, 2015, B936d, P66d, UNC Online

According to European Central Bank estimates, in July 2023, there were about 29.624 billion banknotes in circulation around the eurozone, with a total value of about €1.569 trillion. This series does not have a €500 note, as the ECB have decided to permanently cease its production over concerns that it could facilitate illicit activities.

Estimates suggest that the average life of a euro banknote is about three years before replacement due to wear. But with a wide variation by denomination level, from less than a year for €5 banknotes to over 30 years for €500 banknotes, on average.