The Red Devils, however, remain the highest-ranked Premier League team in the Football Money League - despite seeing revenues drop by £118.1million in 2019-20.
The Money League charted the financial performances of the highest revenue-generating clubs during the disrupted 2019-20 season.
According to Sky Sports, Barcelona top the list ahead of La Liga holders Real Madrid and Champions League winners Bayern Munich, with Manchester United in fourth ahead of Premier League champions Liverpool.
Meanwhile, Manchester United saw the largest year-on-year decline among the top 20 clubs in the Money League. United's revenues are down 19 per cent, to £509million, leaving them behind Barcelona, Real Madrid and Bayern Munich.
They, however, remain the highest-ranked Premier League team in the Football Money League - despite seeing revenues drop by £118.1million in 2019-20.
"The reason for the decrease is predominantly driven by the pandemic, as you can imagine Manchester United with a huge fanbase generate significant amounts of revenue every time they play at Old Trafford," Tim Bridge, director of Deloitte Sports Business Group said.
"They are going to be impacted in a more significant way than many other clubs. Of course, last year they didn't have Champions League football either, so the revenue differential from competing in the Europa League compared to the Champions League had a significant impact on the numbers.
"But caution is needed. With Bayern Munich moving ahead of them, they were able to complete their domestic season in the timeframe, so the numbers for Bayern represent a full year of domestic football, whereas for United they are curtailed."
Among the other PL clubs, Manchester City are sixth in the list, with Premier League clubs Tottenham (ninth), Arsenal (11th) and Everton (17th) also in the top 20.
Overall, the top 20 clubs saw a revenue decline of 12 per cent compared to 2018-19 due to a drop in broadcast revenue and fall in matchday revenue.
Everton, along with Russian club Zenit, were the only two clubs in the top 20 to see an increase in revenue compared to 2018-19.