The deal, which completed earlier this month, is part of an expansion drive by Maxxia's Australian parent McMillan Shakespeare.
Capex has been trading since 1999 and has supported thousands of businesses over the years.
A Square One Law team comprising corporate partner John Hammill and corporate partner and head of banking Mark Lazenby advised the company on the transaction.
Julian Percival, director at Capex, said the Newcastle firm was appointed on the back of industry recommendations. "The support we were given was of the highest quality and they worked incredibly hard within the timescale, particularly over the Christmas period, to complete the transaction," he added.
Hammill said: "Our strong track-record of supporting owners of asset finance brokerages to sell their companies led to us being instructed and we were pleased to work again with Maxxia and its advisers to deliver the deal on time.
"The synergies between Maxxia and Capex are very strong, and I expect both businesses and their customers will significantly benefit from the transaction."
Roger Skinner, chief executive of Maxxia, believes Capex is a "perfect fit".