Ten Hag, now in his second season in charge of Man United, splashed the cash during the summer transfer window to bring the likes of Mason Mount, Rasmus Hojlund and Andre Onana to Old Trafford.
The Man United boss has received criticism in the past for his tendency to target players he has worked with, such as Antony and Lisandro Martinez, who arrived from Ajax last season.
According to a report from the Daily Mail, Vos's Sports Entertainment Group have now become the club's most-used agency when it comes to contract negotiations in bringing new talent to Manchester United.
The report adds that Ten Hag's son Nigel is currently employed by the agency as an analyst.
SEG played a key role in helping to negotiate transfers to the value of £178m for United during a busy transfer window, with Vos being present at the Carrington training base regularly.
Hojlund arrived in Manchester from Atalanta BC for a sum of £72m a month after he joined SEG, while Sofyan Amrabat, who is also represented by Vos's agency, was a late arrival on transfer deadline day.
The Dutch agency was also involved in signing Robin van Persie, Memphis Depay and Daley Blind to United in previous years, but their involvement at the club had dwindled only to resurface following Ten Hag's managerial appointment.