Hi,
The information filled in the form is stored in the user session before the registration process starts so that if something goes wrong (if a required field is not filled, etc), the system can redisplay the form with the information that had been filled in already filled.
Also, after the registration, the user should see an empty page with the success message. That page is displayed by the view file user / after_register.php
So what you can do is edit that view file via the Display>Views menu (you'll see it's almost empty by default) and add such code:
<?php
unset($_SESSION['hikashop_user_data']);
unset($_SESSION['hikashop_address_data']);
unset($_SESSION['hikashop_billing_address_data']);
?>
That will clear the data of the form for the user session.
Note that if you have the user account activation activated (with the link to link in an email to activate the user account after the registration), you'll want to add that code to user / activate.php too.
Note that browsers can also store form data so that the user can easily reuse it later on or even auto fill the form for him:
support.iclasspro.com/hc/en-us/articles/...omplete-Information-