Apply for a certificate of deletion/non-registration from the aircraft register
Source: BUS Rheinland-PfalzA certificate of deletion confirms that the entry for an aircraft has been deleted from the aircraft register.
A certificate of non-registration for a non-registered aircraft confirms that an aircraft is not included in the aircraft register. This certificate applies to brand-new aircraft or aircraft operated only with a Permit to Fly (PtF).
You must apply for both certificates at the Luftfahrt-Bundesamt. You must justify your application and provide details of the aircraft concerned.