Dic: sign off (on something)

• Mary has to sign off on any expenses over $2,500.
• A judge must sign off on a search of anyone's property.
• If all parties sign off, the settlement would end eight years of court battles.

to officially agree to or support something.

Usage notes: often used when someone agrees to something by putting their signature on an official document.

... Cambridge Dictionary of American Idioms,

http://idioms.thefreedictionary.com/sign+off