The Scottish Courts address the hitherto mystery as to what actually is meant by "the basis on which" in respect to a payment notice. Apparently it's good news for payees... Helpful to all if English Cts followed suit (a little certainty in this field would also assist payers no end)

https://www.scotcourts.gov.uk/docs/default-source/cos-general-docs/pdf-docs-for-opinions/2017csoh132.pdf?sfvrsn=0