List of postal codes in the Czech Republic

Postal codes in the Czech Republic consist of 5 numbers, usually written with a space following the third digit (e.g. 123 45).

In general, the first three digits in the postal code represents the city or district. Note that the correspondence between postal code groupings and Czech Regions is not exact.

Prior to the Dissolution of Czechoslovakia these numbers were assigned to regions in Slovakia . Slovakia continues to use these numbers in their own postal code system, meaning that the postal codes of the Czech Republic and Slovakia do not overlap. However, recently the Slovak post office has started planning to use new codes which overlap with the Czech system.

...
Wikipedia