Mandatory conditional field

Hi there,

I set up some conditional fields on my cart process.
If I set those field as required, it is not possible to proceed in case the option to activate them is unchecked.
i.e.
– Do you need invoice?
If yes, then VAT is mandatory
If not, then VAT field does not show, but the cart ask the user to fill this mandatory (hidden) field.

Do you have any suggestion to manage this case?
Thanks for your hints