20880302_ferences__July_2014_FIDE_Laws___FIDE_rule
[0] 7. [USCF rule] A player may stop recording moves for the rest of the time control if the opponent has less than five minutes remaining. If the time control has an increment of at least 30 seconds per move, both players are required to record moves at all times. [FIDE rule] 
You must continue recording moves if you have at least five minutes on the clock, even if the opponent has less than five minutes remaining. If the time control has an increment of at least 30 seconds per move, both players are required to record moves at all times.
The United States Chess Federation - USCF - FIDE Rule Differences (July 2014 FIDE Laws)
FIDE rule