I have a form that our company uses through the API and now we are addind a "Consent to communicate checkbox", however there is no ID in it for us to fill.
Is this not supposed to be filled through the API?
Are you referring to the Notice and Consent (GDPR) form field type? These form field types aren't yet accessible via the Forms API. For the time being, you can add a custom checkbox property that allows a contact to opt in, and use that information to update the contact in HubSpot. This functionality will be made available via the Forms API in the coming weeks, so stay tuned to our product readiness page: