abchandler said:
You aren't expected to keep records of use, so there's no way anyone could tell anyway
In order to benefit from the reduction in tax and national insurance (and VAT if you are able to) you must use your bike for at least 50% of the time for work related travel (including any travel as part of your commute to or from work). You sign an agreement to say you understand this therefore you have no defence if anyone does ever query it. What you are doing by accepting the tax breaks yet not complying with the rules is tax evasion. You have wilfully and with full knowledge neglected to pay taxes for which you are lawfully required to.
You are not expected to keep records however if you never ride it to work then it is pretty easy to tell in that case.
The onus of proof in matters relating to tax lie with the accused and not HMRC therefore the fact that no one can prove you wrong is irrelevant as you have to prove that you did act lawfully in claiming the tax savings.
Any employer who conspires in this is exceedingly stupid as they too benefit from the tax savings and thereby equally guilty of tax evasion whereas if they shut their mouths they are probably well protected by the agreement which the employee signed regarding 50% work related use (including journeys to and/or from work).
As to the moral side well you are abusing the scheme and therefore if it is known that this scheme is being widely abused then we may all lose the benefit of it as the Treasury may just scrap it. That I think is the greater risk in all of this.
The risks are very low however you should be aware of what is that you will be doing.