A permanent number can only be reallocated if the driver associated with that number has not participated in a race for two entire consecutive seasons; for example, a driver picking their number for can not choose numbers which were last used in or , unless the number was issued temporarily by the FIA. For instance, Jenson Button's number 22 would have been available for re-allocation in 2019 after his departure from full-time racing in 2016, but an appearance in the 2017 Monaco Grand Prix replacing Fernando Alonso (who was participating in the 2017 Indianapolis 500 on that weekend instead), meant that his number could not be reassigned until 2020 at the earliest. Yuki Tsunoda subsequently picked that number (22) for the 2021 Formula One World Championship.