When it came to the final vote on same-sex marriage, it was standing room only on the "yes" side of the House of Representatives, while a lonely group of just four "no" voters perched on the other side.

But some MPs were missing from the historic event.

The House of Representatives does not officially record MPs who abstain, but is estimated about 14 MPs did not vote on the same-sex marriage bill.

This included some of Parliament's most high profile "no" advocates, including Treasurer Scott Morrison, former prime minister Tony Abbott and former defence minister Kevin Andrews. Deputy Prime Minister Barnaby Joyce was also among the group, along with renegade Liberal Nationals MP George Christensen, conservative West Australian Liberal Andrew Hastie and Assistant Health Minister David Gillespie.