This is the equivalent of 20 million UK adults if all of the workers who intend to carry over holiday are given permission to do so by their employers.
The research found that employees who plan to shift some of their annual leave to next year will roll over an average of 5.11 days, with 37% of workers intending to take in excess of five days over.
Finder.com said following the average of a full-time employee being paid £117 per day, those who do not take all of their annual leave are essentially working an extra 5.11 days and will be losing out on £598 this year.
However, this will even out over the next year as a temporary law was passed by the government in March allowing workers to carry over up to four weeks of paid holiday due to the impact of the coronavirus pandemic.
In previous years, employees would have lost out on their annual leave income if they did not use all of their leave allowance within that year.
Liz Edwards, consumer advocate and editor-in-chief at finder.com, said: “This temporary law will certainly have helped businesses that were under pressure in recent months - for some companies, people taking their annual leave would have left them short-staffed.
“However, this could be storing up issues for the future, as the pandemic will still be affecting businesses over the next two years, and employees will have surplus leave that they’ll have to take at some point or be paid for it.”
Finder.com warned that businesses will experience the cost of this new law during their next annual leave period when employees are working less for the same pay.
This could cost UK businesses a total of £12bn if all employers allow their employees who want to roll annual leave over to do so.
Londoners plan to carry over the most days this year, at 7.66, with 81% of full-time workers in the capital intending to take at least one day forward.
Workers in East Anglia, meanwhile, are on the other end of the scale, only planning to roll an average of 3.87 days of leave into the next period. This region also has the lowest number of residents (43%) that intend to take leave forward.
Millennials plan to carry over the most days, with full-time workers in this generation planning to take an average of 5.65 days of leave forward. Generation Z, meanwhile, has the largest proportion of employees (76%) rolling annual leave into the next period.
Edwards added: “It’s also important to remember that many people have now been working flat out for months as they have been required to work throughout the pandemic. It’s tempting for people to delay their annual leave with the prospect of being able to go abroad next year or being able to take a longer period of time off. But that is by no means certain, and in the meantime, there's a strong risk of burnout.”
The research was carried out for finder.com by Onepoll from 8 to 10 September 2020. A total of 2,000 people were questioned, with representative quotas for gender, age and region.