1.
If you report back to someone, you tell them about something that they asked you to find out about.
The teams are due to report back to the Prime Minister early next year...
I’ll report back the moment I have located him...
He would, of course, report back on all deliberations...
The repairman reported back that the computer had a virus.
PHRASAL VERB : V P to n , V P , V P on n , V P that , also V n P , V P n (not pron)
2.
If you report back to a place, you go back there and say that you are ready to start work or say that you are present.
The authorities have ordered all soldiers who have returned from the front line to report back to barracks...
They were sent home and told to report back in the afternoon.
PHRASAL VERB : V P to n , V P , also V P for n