Area Code 4001 – Taichung/Changhua

Overview of Area Code 4001 in Taiwan

Area code 4001 is a geographic National Destination Code (NDC) assigned within the Republic of China (Taiwan) national numbering plan, administered under the ITU-T E.164 standard. This code serves the combined administrative regions of Taichung City and Changhua County, located in the central-western part of the island. The geographic allocation follows the national numbering scheme, which uses a variable-length NDC structure. For fixed-line subscribers within this region, the full national significant number (NSN) typically consists of the NDC (4001) followed by a six-digit subscriber number, resulting in a total of 10 digits when the leading trunk prefix '0' is included for domestic calls.

Geographic Coverage and Administrative Jurisdiction

The 4001 code is one of several NDCs that overlay the Taichung–Changhua metropolitan area. Taichung City, a special municipality, is the second most populous urban area in Taiwan and serves as a major economic and cultural hub. Changhua County, adjacent to the south, is an important agricultural and industrial region. The code is used for fixed-line PSTN services, including traditional copper-line and fiber-optic connections, and is assigned to local exchange areas that may span multiple central office codes. Because of the overlay, subscribers within the same geographic region may have different NDCs, and ten-digit dialing is mandatory for all local calls within the overlay area, even between numbers sharing the same NDC.

Dialing Formats and Caller Instructions

For domestic callers within Taiwan, the local dialing format requires the trunk prefix '0' followed by the NDC and subscriber number: 0 4001 XXX XXX. For example, a local call to a fixed line in Taichung would be dialed as 04001 123 456. For international callers, the country code for Taiwan is +886, and the leading trunk prefix '0' must be omitted. Therefore, the international format becomes +886 4001 XXX XXX. For instance, a caller from abroad would dial +886 4001 123 456. It is crucial to note that the NDC is not separated from the subscriber number when dialing internationally; the entire NSN is dialed after the country code.

Overlay Considerations and Number Portability

As an overlay code, 4001 does not denote a specific city or town but rather a service area that may encompass multiple exchanges. This means that a subscriber with a 4001 number could be located anywhere within the Taichung/Changhua region. Additionally, Taiwan has implemented fixed-line number portability, allowing subscribers to retain their numbers when changing service providers. However, geographic numbers are generally tied to the physical location of the line, and porting does not alter the geographic association. For callers, it is essential to always include the full NDC and subscriber number, as local seven-digit dialing is not permitted in overlay areas.

Practical Examples for Local and International Callers

• Local call (within Taiwan): Dial 04001 123 456.
• International call (from abroad): Dial +886 4001 123 456.
• Calling from a mobile phone in Taiwan: Dial 04001 123 456 (the trunk prefix is required).

Understanding the correct dialing procedures ensures seamless connectivity to fixed-line subscribers in the Taichung/Changhua area. Always verify the subscriber number length, as it may vary, but the total NSN after the country code remains consistent.