The option that allows you to change the chassis number in form 576, once it has already been filed, is only set up for social partners. These procedures require an electronic certificate.
You can access all options available for form 576 on the Tax Agency website, by going to 'Registration Tax'. Here you will find the links for filing Form 576 and 'Registration Tax Payment', as well as the specific option to 'Modify the chassis number on a form that has already been submitted (social partners only)', along with other useful links.
If the tax return has not been filed by a social partner, you need to go in person to the corresponding Administration or Delegation to ask for a change of chassis number.