InTouch Games Limited will have to pay £2.2m, Betit Operations Limited is fined £1.4m, MT Secure Trade will pay £700,000 and BestBet Limited faces a fine of £230,972.
The penalty packages relate to failings to effectively safeguard against money laundering and ensure customer protection from gambling harm.
These fines form part of an ongoing look into the online casino sector. In the last 18 months, the regulator says it conducted assessments of, or engaged with 123 online operators. It told 45 of those to submit an action plan to raise standards, with 38 already showing signs of improvement.
Since the start of the investigation, five operators have surrendered their licenses to operate in Britain.
In November, the regulator imposed nearly £14m in penalties to three businesses, for failures to put in place safeguards against money laundering and keep customers safe from gambling-related harm.
Richard Watson, Gambling Commission Executive Director said: “Our work will not stop here. As a regulator, we will continue to set and enforce standards that the industry must comply with to protect consumers.
“We expect operators to know their customers and to ask the right questions to make sure they meet their anti-money laundering and social responsibility obligations.”
