The Te Atatu MP was expelled from Labour's caucus last week after sending an anonymous letter to the media, saying the party couldn't win the next election with Phil Goff as leader and he should be replaced.
Since then senior Labour MPs have questioned Mr Carter's state of mind and said he was suffering from stress.
Labour's national council will meet on Saturday to decide whether to expel him from the party.
Party president Andrew Little said the party was required to observe the principles of natural justice when deciding on Mr Carter's future.
That meant the Labour Party's national council must gather all the information, give Mr Carter a chance to explain, consider the gravity of the claim against him, whether the claim was proven and what sanctions were available.
It was not clear what Mr Carter was being accused of yet.
"We're in the process of doing that at the moment -- formulating what the charges are, so to speak," Mr Little said.
Mr Carter would be told in the next day, or so, which of the party's rules he was accused of breaking.
"Obviously there's a fair few things just coming out of Thursday's events.
"It is quite a process, it's not a question of what particular sanction at this point, it's really a question of ensuring that the process is correct."
It was possible the process would not be concluded at the council's meeting on Saturday if there was not time for the whole process to be worked through, Mr Little told NZPA.
Mr Carter was invited to the meeting. It was up to him whether he attended.
He was also able to send a representative or make a written submission.
The most extreme option for the council would be to expel Mr Carter.
Meanwhile, Mr Carter remains an MP in Parliament but is not a member of the Labour caucus.
Whether he was a Labour MP or a independent MP was a grey area, Mr Little said.
Mr Carter was not expected to return to Parliament this week.
