Long Covid is costing the UK up to £1.5 billion a year in lost earnings after the number of people suffering persistent symptoms of the virus doubled over the last year.
The impact of a rise in long Covid cases from 1 to 2 million is likely to be a significant part of the Pandemic's legacy.
The data from the ONS was used to calculate the number of people who were signed off sick with the loss of 4.2 million working hours.
Employers that pay to cover sick leave would pick up some of the tab for people who stop working because of Covid.
Tom Wernham, a research economist at the IFS and an author of the report, said it was clear from the study that long Covid sufferers have severe effects not only on their health but on their ability to do paid work.
The impact would be felt most by low-income families and workers with pre-existing health problems.
The report said that those who were suffering from the condition were more likely to be claiming benefits and living in social housing.
While previous research has shown that women, those with pre-existing medical conditions and those in poorer parts of the country were more likely to be hit, this is the first proof that long Covid is more prevalent among deprived individuals.
The rising rate of long-term sufferers could put additional strain on families during the cost of living crisis as Covid is more common among poorer families.
According to the report, long Covid can cause workers to take off at least three months after they get sick.
It said that this could mean significant consequences for people without savings or a partner.
The report said that it was difficult to capture some of the changing medical effects of Covid and how it reacts to vaccines, leading it to call for more research to determine the long-term impact of the disease.
The report said that by the six-month mark, the effects are much smaller and most sufferers have returned to work.