Area Code 4004 – Taichung/Changhua

Geographic Coverage and Administrative Jurisdiction

The area code 4004 is a geographic National Destination Code (NDC) assigned within the Republic of China (Taiwan) numbering plan, serving the combined administrative regions of Taichung City and Changhua County. This code is part of the broader 4xxx series that covers central Taiwan, with Taichung being the second-largest metropolitan area in the country and Changhua serving as a major agricultural and industrial hub. The specific allocation of 4004 indicates a numbering pool within the Taichung/Changhua rate center, typically used for fixed-line PSTN and VoIP services.

Dialing Formats and Caller Instructions

For domestic callers within Taiwan, the trunk prefix 0 is used before the area code. Thus, a local number in this region is dialed as 0 4004 XXX XXX, where the subscriber number is typically 6 to 8 digits long, resulting in a total national significant number (NSN) of 9 to 10 digits. When calling from abroad, the country code +886 replaces the leading zero, so the international format becomes +886 4004 XXX XXX. For example, a fixed-line number in Taichung might be +886 4004 123 456. It is important to note that the leading '0' is not dialed when the call originates from outside Taiwan.

Overlay and Numbering Considerations

As of the latest ITU-T E.164 national numbering plan updates, the Taichung/Changhua area has not implemented an overlay code; the 4xxx series remains the sole geographic NDC for this region. However, due to number exhaustion, some new assignments may use different prefixes within the 4xxx range, but 4004 remains a valid and active code. Callers should always verify the complete number, as mobile numbers in Taiwan begin with 09 and are non-geographic, so 4004 is exclusively for fixed-line services.

Practical Usage and Routing

This code is used for both traditional PSTN lines and VoIP services that are registered to a physical address in Taichung or Changhua. For businesses, having a 4004 number establishes a local presence in central Taiwan. International callers should be aware that charges may apply depending on their carrier, and VoIP-to-PSTN calls may have different rates. When dialing from a mobile phone within Taiwan, the same domestic format applies. Always include the area code even when calling from a different mobile network, as Taiwan's numbering plan requires full national dialing for all fixed-line calls.