Keep identifiers as identifiers.
A CSV can contain 00124 correctly while a spreadsheet displays 124. That is a type-conversion problem, not necessarily file corruption.
CSV text does not declare spreadsheet types.
Quotation marks protect separators and line breaks. They do not instruct every spreadsheet to treat a value as text. A UTF-8 BOM helps identify an encoding; it does not preserve leading zeros or numerical precision.
Import deliberately.
- Keep an untouched source copy. Verify that the digits still exist in its text before importing.
- Choose the spreadsheet’s text/CSV import workflow and inspect the separator preview.
- For codes, phone numbers and long identifiers, select a text type where the import interface permits it. Check date-like values too.
- Compare a few known values after import before saving or sending the workbook.
See Microsoft’s guidance on leading zeros and large numbers for its supported Excel versions. Interface options vary. The inspector warns about text patterns; it cannot control your spreadsheet’s import choices.
Do not claim to recover missing digits.
If the exported source already says 124, a general tool cannot know whether it used to be 00124, 0124 or 124. Obtain a fresh export or a documented formatting rule from the source owner.
Formula-like values need a separate decision.
Some spreadsheet applications evaluate fields beginning with =, +, - or @. Ordinary negative numbers can also trigger this conservative warning. FieldWise displays text safely and does not run formulas. It preserves the strings in the download, so only open trusted data in a spreadsheet. It does not insert formulas to force identifiers into text.