Readers' forum: Heads up

I have been approached by a client for tax advice on the heads of terms agreed for a sale of part of their trading company business.

Neither my client nor the other party had sought any professional advice on the deal before agreeing the terms. On further investigation of the circumstances of the proposed sale it occurred to me that there was a much more tax-efficient structure for the deal for both sides than that contained within the heads of terms. Having taken my advice the buyer and seller have now gone away to construct the sale agreement with their respective advisers and I am expecting a tax efficient final agreement.

However on further reflection I started to wonder what would happen if HMRC was to enquire into the deal. Could it request or would it even be entitled to request sight of the original heads...