John, thank you for your reply.
Your suspension from work has laid some conditions on you e.g. you are prohibited to work anywhere else. Not being a lawyer, I am not sure if this is enforceable in law and therefore I am not in a position to express an opinion on it.
To be honest, employers have ways of finding out if you are working elsewhere so you will be doing so at your own risk albeit you intend working further a field. It is probable they may not find out about your additional employment.
Changing of tax code - there are many reasons why your tax code could change, one being if you have more than one employment. Your second employer would most probably tax your earnings using a tax code BR. This code is used when all your income is taxed at the basic rate - currently 20 per cent (most commonly used for a second job or pension).
You wanted to know if you can work again whilst being on suspension without being caught through tax/NI.
Tax matters between HMRC and taxpayer are confidential. They are not shared with employers. If there is a change in your circumstances that give rise to a change in your tax code, the employer is only notified the new code and not details behind the make up of that code. Like wise, the same applies to NI. If you were receiving state benefits and they were means tested then there is likelihood that relevant Government departments would have access of your information through HMRC.
This sharing of information is not extended to your employer or third parties.
Finally, my advice to you would be also to seek opinion from an expert dealing with employment law because of risk involved.
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