Hello Paul, I'm Keith and happy to help you with your question.
The surplus in debtors would be written into the Profit and Loss Account as part of the final knockings. The effect of this would be to reduce the profit of the company, if any, in its final year before winding up. There might well still be a Corporation Tax liability, but without quantifying details I am not in a position to advise.
The reverse effect would be the surplus of funds owed by a subsidiary company being cleared.
If, of course, these are one and the same item then one tends to cancel out the latter.
The distribution by the subsidiary company to a director, if it is not the repayment of a loan by the director to the company, is a remuneration which must be paid through PAYE. Directors are deemed employees of the company and must be paid in such circumstances through PAYE, tax and National Insurance being deducted and rendered to HMRC.
By the way, winding up is a laborious process these days, you can no longer ask the Registrar to merely strike it off the Register. The quick way out is to sell it off as a going concern and you can do this on eBay! If you are going to wind up, and please consider the position of the subsidiary which may, have to be sold out of the group if it is not to be wound up also. It may be a sound idea to use a local, trusted professional to undertake this procedure.
I do hope I have shed some light on your conundrum.