repayment interest from HMRC

sir there seems to be a clear contradiction between what’s there in kaplan study text vs. bpp on the topic of ‘period for which repayment interest is due’:

BPP:
Repayment supplement runs from the original date of payment (even if this was prior to the due date), until the day before the date the repayment is made.

Kaplan:

repayment interest runs
from- later of:
-date tax was due, and
-date HMRC received the tax

to-date of repayment.

do you notice that according to bpp, the interest will accrue from the actual date of payment even if its before the due date, but as per Kaplan the interest would not start running until the due date of tax payment, even if HMRC receives it beforehand.

Am really flustered at the moment. so can you tell which one’s right?