a) a Type Certificate (TC) or (
b) Restricted Type Certificate (RTC), or (
c) Supplementary Type Certificate (STC), or (
d) An approval of a major change or ETSO authorisation.

Below are two useful links regarding applicable regulations, guides and information needed for DOA processes:

Approval of Design Organisation, as described in Part 21 Subpart J of Annex I to Regulation (EU) 748/2012. This applies for those design activities that fall within the scope of EASA’s work, as set out in Article 2 of Regulation (EU) 2018/1139. In these cases, EASA itself is responsible for managing both the approval process and the subsequent supervision of approved design organisations.