Go to Settings › Time & productivity › Manual time.

SettingWhat it does
Require reasonPeople must give a reason when they add time
Require approvalManual time counts only after it's approved
ApproverWho can approve: Admin, Manager, Self, or any mix
Individual settingsAllow or Deny manual time per person, or Deny for all

Keep manual time allowed, with a reason and approval. Turning it off doesn't make the record more accurate; it just hides real work the timer missed.

Manual time settings