A product identifier such as 004817 is a label, even though it contains digits. Letting Excel interpret it as a number can remove its leading zeros. Long identifiers create another problem because Excel numbers have a maximum precision of 15 significant digits.

Keep the original CSV untouched and import into a new workbook. This guide uses desktop Excel for Windows with Get & Transform available. Decide which columns are identifiers and which are quantities before loading; a phone number and an order quantity should not receive the same treatment.

Set identifier columns to text during import

Choose Data, From Text/CSV and open the original file. Enter the query editor using Transform Data or the equivalent Edit control in your version. Select each identifier column and set its data type to Text.

When replacing an automatically inferred column type, use the option to replace the current conversion. Check the preview against the raw CSV before Close & Load. If digits have already been lost in an earlier saved spreadsheet, changing its format to Text will not reconstruct them; return to an intact source.

Microsoft also provides Automatic Data Conversions controls in Microsoft 365 and Excel 2024, but those controls should not be assumed to exist in every older edition.

Check exact characters, not just appearance

Compare several imported identifiers with the source, including one beginning with zero, the longest value and any containing letters. Inspect the formula bar as well as the cell so a narrow column does not hide the full value.

Keep numeric quantities numeric when calculations require them. Do not apply a whole-sheet conversion simply because one column is wrong.

Save the working result as a workbook and retain the original CSV. If you later export for another system, verify the exported identifiers through that system’s import preview or a text view. A workbook that looks correct is only one stage of a reliable transfer.

References: Microsoft: leading zeros and long numbers.