There is an abiding myth it would seem in the community to the effect that an employer is not permitted to re-advertise a job which the employer has previously made redundant for a particular or minimum period of time. This is of course a complete nonsense. There is no particular time limit which applies. The relevance of the point arises in the context of determining whether the original redundancy was genuine. Obviously if an employer renders a position redundant by making a decision to the effect that the employer no longer wishes the job undertaken by anyone (the traditional test which applies to whether a position has become redundant) and then immediately re-advertises for the position to be filled, there will be a strong argument, very difficult for that employer to rebut, that the redundancy was not genuine and was a disguised unfair dismissal. And quite obviously by logic the longer the period between the redundancy and the employer re-advertising the job, the safer the original decision will be from attack, not the least because the unfortunate employee may find himself or herself unable to take action for unfair dismissal due to the statutory time limits which apply to doing so.
However the proper test is always whether the original decision was genuine, and the answer to that will depend upon the circumstances which prevailed at that time, and not later for example by changed economic circumstances. If the business case for the need for the position changes, then so too does the employer’s right to lawfully fill it.