It's non-payment of a salary/wages.
That is seen as the worst sort of debt and if taken to a tribunal and proved you can get the courts to recover the money on your behalf.
What if my employer doesn't pay up?
In a small number of cases, your employer may not pay you the compensation awarded by the employment tribunal.
In England and Wales, there is now a fast track system you can use if you've been awarded compensation by the tribunal but your employer doesn't pay. Under this system, you can ask a High Court Enforcement Officer to act for you to collect the money. You can also fill in a form to ask to have your employer fined.
You can get more information about this from Her Majesty's Courts and Tribunals Service online at: http://www.hmcourts-service.gov.uk.
If your employer doesn’t pay you what you have been awarded, they might have to pay a financial penalty to the Secretary of State.
Section 150 of the Small Business, Enterprise and Employment Act 2015 came into force in April 2016 and imposes fines of up to £5,000 on employers who fail to pay sums ordered by employment tribunals.
You may still want to get more advice from a Citizens Advice Bureau about what to do. To search for details of your nearest CAB, including those which give email advice, click on nearest CAB.
There may be other organisations which can help you. For details of these organisations, see What help can I get with a problem at work