Gaetjens earned a Bachelor of Arts from Flinders University and Graduate Diploma in Accounting from the University of Canberra. From 2015 to 2018, Gaetjens served as Chief of Staff to Scott Morrison. From 1 August 2018 to 2 September 2019, he served as Secretary of the Department of the Treasury. He became Secretary of the Department of the Prime Minister and Cabinet on 2 September 2019, succeeding Martin Parkinson.
Gaetjens signature on Australian banknotes
Gaetjens appears on the following banknotes:
- Twenty dollars 2019 and 2023 (Lowe-Gaetjens)
- One hundred dollars 2019 to 2023 (Lowe-Gaetjens)