One person may appear as a local number, a country-coded number or a spaced and hyphenated number. Without normalization, matching can fail or one contact can become several records. Cleaning should preserve the number's meaning while creating one comparable, deduplicated representation.
A common international target is plus sign, country code and nationally significant number. Confirm the country code first, then remove any domestic trunk prefix required only for local dialing. Keeping an inappropriate leading zero can produce invalid length and failed matching.
The plus sign denotes international form and helps identify already normalized records. Convert 00-style international prefixes consistently if the chosen format uses plus. Whether the final file keeps the plus sign depends on the receiving system, but every row must follow the same rule.
Spaces, hyphens and parentheses improve human readability but rarely carry machine meaning. Remove them along with invisible characters, full-width digits and mixed-language delimiters, preserving only supported digits and the consistently handled leading plus.
Local numbers omit the country code and may contain a trunk prefix. For one known market, missing codes can be added under a documented rule. For mixed-country sources, never apply one code blindly; use source metadata, target market or an existing international marker to classify first.
Apply a fixed sequence: normalize character width, remove whitespace and punctuation, identify international marker and country code, process the local prefix, emit one format and validate plausible length. Early standardization makes deduplication, comparison and exception reporting reliable.
