Ofcom's investigations found Channel 4 in breach of rules surrounding two types of misconduct.
Channel 4 was found to have picked competition finalists before lines had closed in the Richard & Judy “You Say We Pay” competition.
The broadcaster was also found to have operated a so-called “staggered selection” for selecting finalists in both the Richard & Judy “You Say We Pay” and the Deal or no Deal phone-in competitions.
Ofcom said this selection process had created unfair odds that meant viewers entering the competition were not given a fair and equal chance of winning.
In particular, later entrants had a lower statistical probability of being shortlisted as a potential winner, compared to those who entered earlier.