Postal codes in CSV: preserve leading zeros on import
Why a quoted CSV field can still lose zeroes in spreadsheet software, and how to make the import predictable.
Postal codes are text identifiers
A value such as 02108 is not a quantity. Converting it to a number changes the identifier to 2108. Keep the field as text in databases, application schemas, and spreadsheet import settings.
CSV quoting does not declare a type
Quotes protect delimiters and line breaks; they do not require every spreadsheet to import the cell as text. Use the import wizard and set the postal-code column to Text, or use a typed format such as JSON for a programmatic pipeline.
postal_code "02108" "00501" "SW1A 1AA" Expected after import: 02108 · 00501 · SW1A 1AA
Check the whole round trip
Test export, import, edit, and re-export with 02108, 00501, and an alphanumeric code such as SW1A 1AA. Compare the exact strings and watch for trimmed spaces, scientific notation, and locale-specific separators.
Prefer explicit schema in automated jobs
In code, parse the column as a string and validate against a country-aware rule. A valid-looking string can still be unassigned, so keep syntax validation separate from delivery verification.