If you run an aged debtor list and export the info as a csv file then each customers invoice dates do not run sequential.
| Customer Name | Invoice Date | Invoice No. |
| CUSTOMER | 10/04/2018 | 28778 |
| CUSTOMER | 01/05/2018 | 28934 |
| CUSTOMER | 01/06/2018 | 29180 |
| CUSTOMER | 01/11/2018 | 30890 |
| CUSTOMER | 01/10/2018 | 30535 |
| CUSTOMER | 01/09/2018 | 30373 |
| CUSTOMER | 20/08/2018 | 30150 |
| CUSTOMER | 01/07/2018 | 29573 |