Job Vacancy

[pussyfoot]

When a job vacancy arises within the work place, is it compulsory to advertise it internally and externally or is it down to the manager's discretion?

[buildersmate]

It is not a requirement to advertise internally or externally. It may however be a company policy (but policies are not legally binding).
It is isn't typically the recruiting manager's discretion either where to advertise - more typically HR, but depends obviously on the size / scope of the organisation.