You will see and hear the phrase “dormant trust” bandied about a lot, normally in relation to what ongoing duties the trustees of non-active trusts do and don’t have.
Be warned that SARS says that there is no such legal concept as a “dormant trust” and that even economically inactive trusts (which SARS calls “passive trusts”) must be registered for tax, and must render annual tax and other returns, all under pain of stringent penalties for both non-compliant trusts and for their trustees personally. There is a small concession to inactive trusts in that their tax returns are “shortened” and “simplified”.
Bottom line? No trusts are “dormant”, and none are exempted from ongoing tax and other compliance duties.