Hi.I can't really speak for the legality of employing a 13 year old since I'm not a lawyer (but see here). However, I can advise you about the tax situation. Certainly if your son was paid for doing no work, HMRC might if they found out tax your husband on the "wages" paid to your son. Then, the maintenance issue may come to light which would compound his problems.Your husband is effectively trying to get tax relief for his maintenance payments so that other taxpayers are subsiding his outlay. Given the nature of the proposed arrangement, the sole purpose of which is to save tax, I would say that if HMRC conducted an enquiry into the company and it all came to light, he would be accused of having taken part in aggressive tax avoidance, perhaps evasion, and any tax relief he had achieved would be clawed back along with penalties.Take a look here for information on the main tax cases that have set the precedent for looking at the underlying reasons for a series of apparently commercial transactions, the main reason for them having taken place being to avoid tax.If I were you I'd not agree to the plan you outlined. Whether your ex-husband finds another way to achieve his objective would then be up to him and you would not be involved.I hope this helps but let me know if you have any further questions.