You can go back, but as the company has given you a tax free redundancy payment, if they take you back in the same role, both you and your employer would have a tax liability on the redundancy payment as if it was earned income. However, i believe the limit on that is 6 months. But you will find that there is always a way round that - they can employ you on a temporary contract in some capacity i.e. a slightly altered role, until the 6 months expires and then you can be re-employed with hopefully no tax liability on any side.