The problem occurs when the user returns to that form, and the previous data entries remain,
The "previous data entries" remain because the are in the table.
Forms do not "have" data. Forms are a way to view the data stored in a table.
If you have a bound form (sounds like you do), you can set the form to "Data Entry" mode. This allows you to add new records, but cannot view existing records (in that form).
Option two is to move to a new record. either on form open or on a button click.
Code:
DoCmd.GoToRecord , , acNewRec