Telephone numbers in Liechtenstein

Country Code: +423 (formerly +41 75)
International Call Prefix: 00
Trunk Prefix: None

Liechtenstein used the Swiss telephone numbering plan (+41) under area code 075 (formerly dialed as +41 75 from outside Switzerland & Liechtenstein), but in April 1999, it adopted its own international code +423, meaning that calls to and from Switzerland require international dialing. It is dialed internationally as +423 xxx xx xx.

...
Wikipedia