on (one's) (own) head be it

on (one's) (own) head be it

The blame, consequences, or responsibility of a risky, dangerous, or foolish decision or action belongs to someone and no one else. If she wants to quit a high-paying job to chase after some fantasy of being a travel writer, then on her head be it.
See also: head, on
Farlex Dictionary of Idioms.

on your head be it

or

on your own head be it

mainly BRITISH
You say on your head be it or on your own head be it to tell someone that they must accept the consequences of a particular action. This is not the time for such a discussion. But if you insist, on your head be it. If you choose to ignore my generous offer, then on your own heads be it.
See also: head, on
Collins COBUILD Idioms Dictionary, 3rd ed.

on your (own) head be it

used to indicate that you think someone should take full responsibility for anything that goes wrong if they persist in an inadvisable course of action.
See also: head, on
Farlex Partner Idioms Dictionary

on somebody’s (own) head ˈbe it

(often used for warning somebody) somebody is alone responsible for the results of their action or decision: You refuse to go to your own daughter’s wedding? On your head be it! On his own head be it if he decides to leave college early.
See also: head, on
Farlex Partner Idioms Dictionary
See also:
  • cost (someone) dearly
  • dearly
  • a fool and his money are soon parted
  • fool and his money are soon parted
  • fool and his money are soon parted, a
  • parted
  • doofus
  • a mug's game
  • be a mug's game
  • a practical joke