Laws of the Game
3. Allowance for time lost
Allowance is made by the referee in each half for all time lost in that half through:
assessment and/or removal of injured players
medical stoppages permitted by competition rules e.g. ‘drinks’ breaks (which should not exceed one minute) and ‘cooling’ breaks (ninety seconds to three minutes)
delays relating to VAR ‘checks’ and ‘reviews’
any other cause, including any significant delay to a restart (e.g. goal celebrations)
The assistant official indicates the minimum additional time decided by the referee at the end of the final minute of each half. The additional time may be increased by the referee but not reduced.
The referee must not compensate for a timekeeping error during the first half by changing the length of the second half.