In some rural fertility clinics and other states that limit is cut to five families for each donor, due to the potential for meeting related families and future contact with a donor.
Along with donating through registered clinics, the 40-year-old has also been donating informally through an online group called Sperm Donation Australia.
When going through formal channels, a donor must confirm they have not donated over the 10 family limit.
Mr Phan donated sperm to Melbourne clinics Number 1 Fertility and City Fertility, according to the Daily Mail.
VARTA Chief Executive Officer, Louise Johnson, told the publication that the investigation into Mr Phan meant that one patient at the Number 1 Fertility facility has now been barred from using her embryos created with the Brisbane man's sperm, causing her immense distress.
"Once a treating clinic knows that more than 10 families have been formed through one donor's donations, they cannot keep using that donor's sperm," Ms Johnson said.
"In addition to this when a donor reaches the 10-family limit the clinic cannot use embryos already created using his sperm for a recipient who has not already had a child using that donor's sperm."
Ms Johnson said it was "incredibly sad and naive" of Mr Phan to continue to donate his sperm, adding it is against the law to "provide misleading information to a clinic as part of a consent process to donate".
Speaking to Kidspot in October this year, Mr Phan said he first thought about donating after he and his wife, Merlyn, were at a fertility clinic while trying to get pregnant with their second child.
At that point Mr Phan was unsure if he was infertile and decided that if he wasn't he would help others by donating.
He said when he first started donating his plan was to only donate nine times.
"I reached my ninth and I thought that was it. Then I received a message from a lady around Christmas saying the donation was successful, which then became my tenth and I thought, 'Well I've already gone over my limit, I'll just help a few more' and it kind of blew out. Some of the original recipients weren't too happy about it," he told the publication.
Mr Phan said when he first started donating he was the only Vietnamese man in Australia doing so.
"I didn't think anyone would want me as their donor to be honest," he said.
"I was pretty surprised at the amount of interest I received."
Some weeks the 40-year-old will have three people contacting him in 7 days asking for donations, with some woman flying from Sydney and Melbourne to have Mr Phan as their donor.
Speaking generally, Professor Fiona Kelly from La Trobe University Law School said because private sperm donations have become so popular, most online donors were exceeding their donation limits.
"Clinics are supposed to pick up if a donor is donating privately as well as at the clinic," she told the Daily Mail.
Professor Kelly said some of the donors were going into the process with a mindset other than helping people create families.
"These men are intending to donate to a large number of people and the goal seems to be prolific, rather than build a relationship with a small number of recipients," she said.
