Because of their historical connections with Unitarianism, they are known particularly for allowing dissent from Trinitarian doctrine (the belief that God exists as a Trinity).
However, these Free Christian groups also welcome people who adhere to more orthodox beliefs, as the emphasis is on theological inclusivity rather than non-conformity per se.
In Britain the term "Free Christian" can be traced back to the ministry of James Martineau in the late 19th century.
Martineau was an advocate of theological inclusivity, arguing that explicitly Unitarian churches would lead to "a different doxy" from orthodoxy.
The Non-subscribing Presbyterian Church of Ireland, an independent denomination in its own right, no longer has any institutional link with the GAUFCC and UCA (the NSPCI disaffiliated from the UCA in 2015); although some NSPCI ministers trained through their theological and ministry training colleges.