I am sure some one will know the answer to this, we are just taking over premsies with air conditioniong which are managed by landlord, We have a certificate form the landlord to state thet the air con unit has been tested i believe this is a five yearly test, what is the time scale for legionella testing?

is it included with the 5 yearly test? or should it be completed every year ?

This all depends on the type of air conditioning system that you have in place. If its a office building with a closed system that has a fan unit outside and a wall / ceiling mounted unit inside and is cooled by a refrigerant, then the likelihood of legionella is slim and should be described within your risk assessment, as if someone has a health condition, that could be affected by a small dose of legionella bacteria, then this should considered in any investigations, but for actually regular testing for legionella, this is not a common practice, it can be done but it is very costly.
If the air conditioning system is where the air is cooled by passing through a water system, then regular checks on that water need to be carried out as described by Ron, which would also be supported with the water tank temperature checks on a regular basis. As the water temperature within stored systems has a big part to play with the concentration of the bacteria
A risk assessment is required under L8, and review after any alterations to the system or after 2yrs, by a competent person.

Thanks for the information, the responsibility for the aircon unit and related testing and maintenance has now been accepted by the facilities department that manage the premises.
Which is a load of my every increasing in tray

The 5 yearly inspection of systems over 12kWh (could be a single unit or a combination of units) is with regards to the energy efficiency of the system – nothing to do with legionella.
Phil