Bodnar
There is no specific requirement for a claimant to notify the DWP if they start work while receiving PIP, however it may count against you if you do not do so and the DWP are concerned as to whether your award is still valid.
Basically the issue will be whether your starting work contradicts any of the limitations that you stated on your PIP2 form, so as a couple of examples; you stated that you have incontinence problems and you are intending to work as a cahier in a supermarket, would this cause issues with you accessing a toilet as needed, or, you have said that you have problems going out, how will you cope travelling to and from work.
If you think that there is the potential for these type of concerns to be raised then you should give serious thought to notifying the DWP, you can explain the limits of this work and how you intend to manage, this may be sufficient for the DWP, but they may request additional details and it may result in a re-assessment.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems