The tribunal said Voordouw had signed a series of statutory declarations last year saying all bank balances and cash books were reconciled. But the tribunal said those declarations were incorrect.
Mason became aware last August that up to $1m and a further $200,000 had been transferred out of the trust account.
Yet neither of the two men notified the Real Estate Authority of the discrepancies, the tribunal found.
There were no allegations in the case that either man had misused client funds, the tribunal said.
Voordouw said he had relied in good faith on experienced and competent accounting staff to ensure documents were correct. The men described a series of meetings, emails and assurances given about the money.
The tribunal did not find the pair had engaged in misconduct as being reckless or a wilful breach of the Act, but did find the pair were "seriously incompetent or seriously negligent".
Both men have the right to appeal to the High Court.
Harcourts has been contacted for comment.