Judge Goldspring said one of the accounts had been used to move money in relation to the allegations.
“I am satisfied that this account is used for payments connected to female complainants in the Romanian allegations and also significant payments to co-defendants in the Romanian criminal proceedings,” he said.
“Whether or not the respondent brothers’ webcam business activities amounts to modern slavery (and other) offences will ultimately be determined by the Romanian criminal courts.
“But for these purposes, I am satisfied that none of these funds were declared to the tax authorities in either the UK or Romania.”
He said this supported his conclusion that the brothers’ “entire financial arrangements are consistent with concerted tax evasion and money laundering”.
When the pair were initially accused of hiding the cash from tax authorities, they had told the court they would rely on evidence from an expert accountant.
That plan was later abandoned and Judge Goldspring said they ultimately provided no evidence to counter the police’s allegation.
Devon and Cornwall Police said it welcomed the judge’s decision.
A force spokesperson said: “From the outset we have aimed to demonstrate that Andrew and Tristan Tate evaded taxes and laundered money through bank accounts located in Devon.
“Both individuals are alleged to have concealed the origins of their income by channelling money through ‘front’ accounts, constituting criminal activity and rendering those earnings proceeds of crime.
“We will refrain from further comment until the 28-day appeal period has concluded.”
Separately, Bedfordshire Police is seeking the extradition of the Tate brothers to the UK in relation to allegations of rape and human trafficking, which they deny.
A judge in Bucharest has said that extradition request will be dealt with after the conclusion of the case in Romania.
