| NPA | CHAR (3) | Numbering Plan Area code, the first three digits of a 10 digit North American Numbering Plan (NANP) number, commonly called the Area Code. |
| NXX | CHAR (3) | Central Office Code, the first three digits following the Area Code in a 10 digit NANP number, commonly called the telephone exchange or prefix. |
| BLOCK_ID | CHAR (1) | Block identifier. Implies, represents, or identifies either the entire group of 10,000 numbers or a specific group of 1,000 numbers within the NPA NXX. |
| TBP_IND | CHAR (1) | Thousands-block pooling indicator. |
| LATA | CHAR (5) | Local Access and Transport Area (LATA), or LATA-like code of the Rate Center. |
| LTYPE | CHAR (1) | Identifies whether the primary use of the NPA NXX is wireless or landline based on its initial assignment. |
| CONTAM | CHAR (1) | For pooled numbers, specifies whether the thousands-block allocation is contaminated (i.e. the block contains at least one number that cannot be assigned). |
| STATE | CHAR (2) | State or province postal abbreviation of the Rate Center locale. |
| COUNTRY | CHAR (2) | ISO 3166-1 Country Code of the Rate Center locale. |
| WC | VARCHAR (128) | Name of the Serving Wire Center, also referred to as the Wire Center, Central Office, or exchange. Decoded from the first 8 characters of the switch CLLI code, this field will identify at a minimum the city location of the telco switch. The Wire Center identifies where service for a particular NPA NXX originates from which may be different than the NPA NXX service area. |
| SWITCH | CHAR (11) | The Common Language® Location Identifier (CLLI) code of the telco switch serving the NPA NXX. This field is generally present for all United States and Canadian records. For NXXs in the Caribbean and Bermuda NPAs, the SWITCH field may be populated with SWCHxxUNKNO, where xx identifies one of the countries or territories in the Caribbean or Bermuda. |
| RCSTATUS | VARCHAR (2) | Specifies whether Number Pooling is required within this Rate Center. Currently applies to United States entries only. |
| RCTYPE | CHAR (1) | Identifies whether the Rate Center is a zoned or non-zoned Rate Center. |
| RC | CHAR (10) | Industry standard Rate Center Name Abbreviation. |
| RCV | INTEGER | The four or five digit V&H coordinate system vertical coordinate of the Rate Center. |
| RCH | INTEGER | The four or five digit V&H coordinate system horizontal coordinate of the Rate Center. |
| RCLONG | VARCHAR (128) | Full name of the geographical Rate Exchange Area, commonly referred to as the Rate Center. A Rate Center identifies the geographic area (i.e. locality, town, or city) served by a particular NPA NXX combination. |
| TZ | CHAR (2) | Time zone of the Rate Center locale. |
| DST | CHAR (1) | Y/N flag indicating whether daylight saving time is observed. |
| ZIP | VARCHAR (5) | 5-digit United States ZIP or 3-character Canadian Forward Sortation Area code for the Rate Center locale. |
| ZIP2 | VARCHAR (5) | Second possible ZIP or FSA code |
| ZIP3 | VARCHAR (5) | Third possible ZIP or FSA code |
| ZIP4 | VARCHAR (5) | Fourth possible ZIP or FSA code |
| FIPS | CHAR (5) | United States FIPS county code or Canadian Census Division code. |
| FIPS2 | CHAR (5) | Second possible FIPS or Census Division code |
| FIPS3 | CHAR (5) | Third possible FIPS or Census Division code |
| CBSA | CHAR (5) | United States Core Based Statistical Area (CBSA) or Canadian Census Metropolitan Area (CMA) code. |
| CBSA2 | CHAR (5) | Second possible CBSA or CMA code |
| MSA | CHAR (4) | Historical 4-digit Metropolitan Statistical Area (MSA) code of the MSA the Rate Center is located in. MSA codes have been replaced with the 5-digit CBSA codes. |
| PMSA | CHAR (4) | Historical 4-digit Primary Metropolitan Statistical Area (PMSA) code of the PMSA the Rate Center is located in. PMSA codes have been replaced with the 5-digit CBSA code. |
| LATITUDE | DOUBLE | Latitude in decimal degrees of the general NPA NXX service area. |
| LONGITUDE | DOUBLE | Longitude in decimal degrees of the general NPA NXX service area. |
| OCN_CATEGORY | CHAR (1) | Identifies the general company/carrier "type" of the OCN. |
| OCN | CHAR (4) | 4-character Operating Company Number (OCN) also known as a NECA Company Code, identifying the NPA NXX code-holder or block-holder. |
| DERIVED_FROM_NPA | CHAR (3) | Indicates the previous NPA that existed in the area covered by a given NPA. In cases of overlays, some or all of the previous NPAs may still cover the area. The OVERLAY field should be referenced to determine how to interpret this field. |
| NEWNPA | VARCHAR (20) | Specifies the new area code to be used with the NXX or new area code(s) created in the same coverage area as the current area code. The OVERLAY field should be referenced to determine how to interpret this field. |
| OVERLAY | CHAR (1) | Single character field to determine how the DERIVED_FROM_NPA and NEWNPA fields should be interpreted. |
| MTA1 | INTEGER | Major Trading Area |
| MTA2 | INTEGER | Second Major Trading Area |
| BTA | INTEGER | Basic Trading Area |
| NXXTYPE | CHAR (2) | 2-digit code identifying the function that the Central Office Code (NXX) or Thousands Block is performing. This field further defines the service type specified in the LTYPE field. |
| OLSON | VARCHAR (128) | Internet Assigned Numbers Authority (IANA) time zone database time zone identifier or time zone name for the Rate Center geographic location. The IANA time zone database is also referred to as the tz database, the zoneinfo database, and the Olson database. |
| UTC | CHAR (6) | The standard time Coordinated Universal Time (UTC) offset at this location. Format is +\-HH:MM. |
| LIR | VARCHAR (128) | Name of Local Interconnection Region rate center is assigned to if any. |