Not only that and that alone.
Now that days of arrival and departure to and from the UK can be counted as resident days (recent High Court case re: Seychelles domiciled UK citizen claiming non residency) commute jobs are harder to wash through the revenue as non resident occupations.
The Revenue and Customs have now become pretty thorough and have the right to impose back taxes, compound interest on top of that, apply a fine of up to 100% and go back twenty years if they believe that fraud is involved. Obviously, failure to declare world wide income for UK tax purposes could be construed as fraudulent.
The tax free salary offered by so many agencies is probably only tax free to you in the country in which it is paid. You, the beneficiary are not necessarily tax free. It is your problem to sort out with the revenue in your country of residence. Proper advice from a suitable source would be a very sensible idea?
