You can delete previously used bill profiles, as long as there are no customer profiles associated with the profile.

Once all profiles (including inactive) have been moved off of the profile, go to Settings ⚙️ > Billing > Customer Billing Profiles

Select the profile to view the details and select the delete option in the lower left hand corner.

If the delete option is not available, this indicates there is at least one customer profile associated with the bill profile.

An easy way to identify customers associated with that profile is through your Billing page.

Or though reporting. If you do not have a customer bill profile report, please contact support or your Implementation Manager