To whom it may concern
I confirm that (name) is/was employed as (position) with this organization from (date) to (date/the present day), and was/is paid (salary, plus bonus and benefits as applicable).
Their job of (position) carries the following responsibilities (describe briefly the job). (Name) is skilled in (details of skills) and is also (characteristics - e.g. reliable, a good communicator, team spirit etc).
I would happily re-employ (name) as I consider him/her to be a valuable member of the team, who consistently achieved good results and delivered all expectations.
Sincerely,