So this is a little bit of a garbled description of something that's been described in the Sharpe novels (about a British rifleman in the Napoleonic period). The plot point there is that soldiers would enlist in the army and would be paid a shilling (hence "Taking the King's shilling" as a metaphor for joining the army), and that accepting the shilling would in effect oblige the men to join the army. In the (fictional) Sharpe's Regiment, an unsavory recruiting sergeant slips shillings into recruits' beer so that when they fish them out, he has them under his power. It's definitely a story that's been repeated a lot in different forms -- Terry Pratchett has this done to, if my sources are reliable, trolls in Monstrous Regiment.

Impressment in the Navy worked differently -- I wrote about this more here -- but there was a time period in which sailors were paid a sum of money, known as an "imprest," before needing to show up to service. This changed over time as the Navy's needs changed -- eventually they'd just drag you on ship.