Background and aims: Inducements are a core component of gambling marketing. They have attracted increased attention from regulators due to their potential links to gambling harms. We deployed a randomised, pre-registered online experiment to test whether inducements cause specific changes to gambling behaviour. Methods: 622 males aged under 40 made incentive-compatible betting choices over Euro 2024 football matches. Participants were randomised to see bets with inducements or to a control group with no inducements. Some participants were also randomised to see inducement-linked bets where the expected value odds made them the worst available choice, i.e., a dominated option that was an objectively ?bad bet" even accounting for the inducement. Results: Inducements increased the amount spent on bets by over 10% and almost halved the number of people opting not to bet. Those with evidence of problem gambling were disproportionately affected. Inducements also led to decision errors, making bettors three times more likely to choose bad bets. Discussion and Conclusions: Our findings add to growing evidence that inducements risk causing harm to consumers, with worse effects among those with evidence of problem gambling. We provide novel evidence that inducements push gamblers into making decision errors, opting for bad bets that heighten the risk of financial harm. Our findings support the regulation of inducements to reduce gambling harms.  Kulcsszavak: inducement, betting, problem gambling, gambling regulation, free bet, money back offer