[GNC] Best way to link an overpaid invoice and credit note?

[Dr. David Kirkby]

I have 4 transactions in my GnuCash accounts to a vendor RS with whom I
have an account, and must pay by 20th of the following month. The amount of
all the transactions is entered correctly, with a total of £322.70. I then
put one payment in GnuCash, which was a split payment for all 4
transactions. However, when actually paying RS from my mobile banking app,
I paid £332.70 instead of £322.70. So there's an overpayment of £10. So
when RS invoiced me again, it they have deducted £10 due to the
overpayment.

I don't know the best way to handle this. I obviously need to change the
payment in GnuCash to be £10 more than before. But I'm unsure how I can now
pay those 4 transactions, plus an extra £10, unless I delete them all, then
try to pay the 4, but change the amount GnuCash suggests, to an extra £10.

Should I unpost them? I was thinking of creating an asset account, and
calling it something like 'credit notes', and moving the £10 to there. But
next time I pay RS, which will be for several hundred pounds, how could
GnuCash be told to credit the credit note by £10, and credit the bank
account by the rest?

Dr David Kirkby Ph.D
Email: drkirkby at kirkbymicrowave.co.uk Web:
https://www.kirkbymicrowave.co.uk/
Kirkby Microwave Ltd (Tel 01621-680100 / +44 1621-680100)
Stokes Hall Lodge, Burnham Rd, Chelmsford, Essex, CM3 6DT.