Hello and thanks for using Just Answer.
My name is ***** ***** am happy to assist you with your enquiry.
You are indeed correct in feeling uncomfortable with this arrangement. Although your Agents may not appreciate the potential consequence, your Solicitor will certainly not be prepared to proceed on this basis unless you can provide to him a list of the fixtures/fittings together with an estimated value to show that they are indeed worth £50,000. Without you providing this list, the Solicitor will not proceed, and will advise you that even if he did, you (and him), together with your Buyer are all guilty of tax evasion, which is punishable by a prison term!!
HMRC have 12 months from completion to investigate any Stamp Duty queries, and they ar eentitled to request from your Solicitor a copy of the Contract, which will show what additional price you have sold any fixtures and fittings for. So, unless there is a suitable price list attached to the Contract itemising the fixtures, they may well ask further questions.
So, please don't do it- it is not worth the risk, and as I have said, your Solicitor should refuse to proceed on this basis even if you were prepared to take the risk.
I hope this assists you and answers your question.