When you open a downloaded report in Excel, Excel strips any the leading 0s.
You can resolve this issue by following these steps.
1. Open a new spreadsheet in Excel.
2. On the ribbon, go to the "Data" tab.
3. Under "Get External Data" choose "From Text."
4. Choose the CSV file you downloaded using the file browser that appears and click import.
5. In the "Text Import Wizard" choose "Delimited" and the "My Data has Headers" checkbox, then click next.
6. Under Delimiters, ensure "Comma" is checked and click "Next."
7. You will see a preview of your data. Choose the column that contains the registration numbers and using the "Column data format" section above, select "Text."
8. Click "Finish" then "OK."
9. Your data should now display with the leading 0s.