Since you want all of your employees to sign an acknowledgement form, the best time to have them sign one is at the start of employment. Include the signing of this form as part of their onboarding process. But make sure you provide them with adequate time to read the handbook fully (usually a couple of days). Remember that if you make significant changes to the handbook, it’s safest to have all of your employees sign new handbook acknowledgement forms as soon as the new handbook is released.