The rules say you have to register to vote every few years. If you're in the Services, then Hackle's points below make it more difficult.
We don't believe that either the registration system or the voting arrangements allow sufficiently for the real-life circumstances of the Armed Forces, especially with current commitments. That is why campaigners are calling for sensible improvements to the system, as well as maximum effort on making the present arrangements work.
In theory, the requirement since 2001 to re-register annually is the same for service personnel as for any civilian voters. Re-registration for ordinary voters is a straightforward matter of signing and returning a simple form which is sent out annually. In practice, if the form is not returned in due time, ordinary voters are thought much more likely than service voters to have their names kept on the electoral register. Also, some Councils offer freefone and on-line re-registration - which is not available to registered "service voters".