Tax refund where wages unpaid

I have been trying to help my son get the correct tax refund. In January this year his employer a ( very small) limited company ceased trading, after unfortunately the sole director and shareholder died. Those looking after the estate declined putting the company into a formal insolvency process, trying (but failing) to get the company struck off. The person responsible for the payroll filed for the January month for the company, but this was never paid( nor will it be as there are no assets). This means the staff have been taxed on money they never will receive which is extremely unfair and cannot be right? We filed for a tax refund as my son’s earnings exceeded his personal allowance and he could not work for the remainder of the tax year due to health issues. The “income” he received for January (that was never paid) was taxed in the HMRC calculation which had the effect of reducing the refund he has since received by the amount of tax suffered in this unpaid payroll. Have tried several times explaining this to HMRC through the Personal Tax Account window, but cannot get an answer. Is he entitled to a refund of tax suffered on a payroll that was never paid? It seems extremely unfair on him and any other staff if that is the case.

Hi,
We cannot answer this question as we need access to your records, can you please therefore contact  the HMRC helpine:
Income Tax: general enquiries
Thank you.