have your hand in the till

have (one's) hand in the till

To be stealing money from one's workplace or employer. Margaret had her hand in the till for years, but she finally got caught after she claimed her two-week trip to Paris as a business expense.
See also: hand, have, till
Farlex Dictionary of Idioms.

have your hand in the till

or

have your fingers in the till

mainly BRITISH
If someone has their hand in the till or has their fingers in the till, they are stealing from their employer or from an organization they are involved with. Thirteen company directors were found with their hands in the till in the first quarter of this year. There are rumours that a number of officials have had their fingers in the till. Note: You can also talk about people being caught or found with their hands in the till or with their fingers in the till. He got caught with his fingers in the till once too often. Note: The usual American expression is catch someone with their hand in the cookie jar.
See also: hand, have, till
Collins COBUILD Idioms Dictionary, 3rd ed.

have your ˌfingers/ˌhand in the ˈtill

(British English, informal) steal, especially small amounts of money from a shop/store, business, etc. where you work: He lost his job after they found he’d had his hand in the till.
See also: finger, hand, have, till
Farlex Partner Idioms Dictionary
See also:
  • a change of heart
  • appear to
  • (one's) game
  • a mystery to (one)
  • a turn of phrase
  • able to do
  • able to do it
  • a shoulder to cry on
  • a piece of the action
  • a piece/slice of the action