“Effective 15 September 2025, the postcode of the registered office address will be a mandatory field for the Companies House Service (CHS) Filed AD01 form used to change a company’s registered office address.
The updated API resource for changing the registered office address (Create a registered office address resource) will require the postal_code field in the request body from this date. To prepare, please ensure your implementation of the registered office address resource includes a postal_code field in all relevant requests.”