Go to the website and create a form.

Select the Action as Create a customer.

Note: The eCommerce app needs to be installed to get the option to create a customer from a website form.

Alternatively, the form can also be enabled from contacts with the studio. Please refer to the below post for this.

https://www.odoo.com/forum/help-1/creating-a-website-form-for-a-new-model-240246

Add a field on the form and select the “Is a Company” existing field.

This field dictates if the contact is a Company or an individual.

Enable the Default Value which enables the checkbox and would make the contacts created from the form is a company.

Set the Visibility as “Hidden” That way the website visitors will not be able to see the field.