HM Revenue and Customs raided a Blackwood arcade and seized 36 illegal gaming machines.
Excise officers visited the amusement arcade and seized the unlicensed gaming machines containing.
The raid by officers was one of four with others taking place in Cardiff, Gloucester and Taunton.
In total, £24,000 in cash was found in 85 machines.
HMRC spokesman Bob Gaiger said: “We are investigating the non-payment of at least £180,000 in Amusement Machine Licence Duty over a three year period. Gaming machine operators are legally required to pay the excise duty on each machine to purchase the appropriate licence. If they don’t, then our officers step in. We only seize machines as the last resort, when all other efforts have been exhausted.”
Another spokesman added that due to an ongoing investigation, HMRC could not say which amusement arcade in Blackwood had been raided.