Retaining leading zeros in an excel file can be tricky. We suggest you format this data as a custom text field, instead of numeric in your spreadsheet.
- Open your spreadsheet as Excel format
- Save the cells as Text Format so that the leading zero sticks
- Save the file as a CSV format
- Import the CSV into your account
- Map the column in question to an available Text field (example, Text1_)
- Check Contact records to verify 0 was retained