Firms are being urged to be flexible with staffing as workers plan how to watch their teams in the Euro 2016 football tournament, which starts on June 10.
The conciliation service Acas launched new guidance to help employers prepare for potential issues, and avoid workers being given a "red card" for sloping off.
Acas said firms should have agreements in place to cover requests for time off, sickness absence, website use during working hours or watching TV during the tournament, which runs until July 10.
Some games, including the crunch encounter between Wales and England, are being held in the daytime.
Sir Brendan Barber, who chairs Acas, said: "There's another very important European event happening next month where passions are likely to run high between supporters of various sides. The Euro 2016 tournament is an exciting event for many football fans but staff should avoid getting a red card for unreasonable demands or behaviour in the workplace during this period.
"Many businesses need to maintain a certain staffing level in order to survive. Employers should have a set of simple workplace agreements in place before kick off to help ensure their businesses remain productive whilst keeping staff happy too.
"Our guidance published today can help managers get the best from their team players, arrange appropriate substitutions if necessary and avoid unnecessary penalties or unplanned sendings-off."
Acas said a possible option is to have a more flexible working day, with staff starting work later or finishing early and then agree when this time can be made up.
Employers could also allow staff to take a break during match times, it was suggested.