"In the context of estoppel by convention, the question here is whether the party estopped actually (or as reasonably understood by the estoppel raiser) intended the estoppel raiser to rely on the subscription of the party estopped to their common view (as opposed to each, keeping his own counsel, being responsible for his own view)."
"(1) An inquiry extends to anything contained in the return, or required to be contained in the return, that relates - (a) to the question whether tax is chargeable in respect of the transaction, or (b) to the amount of tax so chargeable. …"
"(1) An inquiry under paragraph 12 is completed when [HMRC] by notice ('a closure notice') inform the purchaser that they have completed their inquiries and state their conclusions. (2) A closure notice must either - (a) state that in the opinion of [HMRC] no amendment of the return is required, or (b) make the amendments of the return required to give effect to their conclusions. …"