Can you please clarify the differences between Forms 18A, 18B, 20A and 20B?
EASA Form 18a (form to be created by the design organisation, see AMC 21.A.263(c)(6)): This Form shall be used by the design organisation only when procedures have been developed by the DO to support the privilege of 21A.263(c)(6) and within the related scope.
EASA Form 18b (included in form FO.CERT.00037): This Form shall be used by Non DOA, or by design organisations not holding the privilege.21.A.263(c)(6).
EASA Form 20a (form provided by respective NAA): This PtF Form shall be used by the design organisation when the DO does not hold privilege 21.A.263(c)(7). The Form 20a will be then submitted to the NAA of the country of registration of the A/C who will issue then the PtF.
EASA Form 20b (form to be created by the DO, see Part 21 - Appendix IV): This PtF Form shall be used by the design organisation when the DO holds the privilege 21.A.263(c)(7). In this case a copy of this PtF shall be submitted to the competent NAA at earliest opportunity but not later than 3 days after issuance of the PtF.