The amount that operators must make before paying more in gaming duty will rise as a result of the gross gaming yield (GGY) bands being adjusted to reflect inflation.

The minimum rate under current UK law is 15% on an operator's first £2.5 million ($3.5 million), and it increases to 50% on earnings exceeding £13.8 million. This was codified in section 108 of the Finance Act 2021, amending previous legislation from 1997. However, it is still vulnerable to change, as casinos firms will only pay the 50% maximum on anything over £14.6m, and will instead pay 15% on their first £2.6m.

A progressive tax structure governs gaming duty, meaning that taxpayers pay at marginal rates determined by their income—that is, those with higher incomes pay more.

"Casinos pay gaming duty on their gross gaming yield (GGY), which is generally the sum of their customers' bets less their winnings. The GGY bands are used to compute the duty. HM Revenue & Customs (HMRC) noted that the rate used to compute the levy increases in tandem with the GGY.

It is hoped that this method will preserve true amounts of gaming duty accounted for by casino operators. About fifty casino operators are anticipated to experience a "negligible impact," and "minor changes" to HMRC's IT systems are estimated to cost about £30,000.

A bill to raise the GGY values in section 11(2) of the Finance Act 1997 will be proposed in Finance Bill 2021–2022. Businesses subject to gaming duty are obliged to file a return at the conclusion of each period, use the GGY bandings to determine their gaming duty liability. These bandings span a six-month accounting period.