An ex-employee has applied for a vacant role, what should I do?
If someone has left your business and then subsequently applies for a vacant position, there is no legal entitlement for them to be considered as a priority candidate. If they were a poor performer, or you had any other concerns about their employment, you may choose not to shortlist them or bring them in for an interview but you would need to make sure that your decision was not discriminatory.
Job applicants are protected by discrimination laws so if, eg the ex-employee had high levels of absence which deters you from considering them for the role, you may be at risk of a discrimination claim if their absence was related to a disability or pregnancy. If you do re-employ an ex-employee, their continuous service will start again from zero which means they may not be entitled to the contractual benefits that they previously enjoyed, until they have been with you long enough in the new employment to accrue those benefits again. This applies unless the break in between both periods of employment is less than one week.