Moving transactions retrospectively

[Mike or Penny Novack]

OK, if immutable, then maybe the way to proceed is the way it would have 
had to be done in the old days of pen and ink on paper in bound books 
where an existing entry was also never changed.

Instead, an offsetting/correcting transaction entered.

OK, suppose we have an income account X with ten transactions there 
where the other side of the transaction was A/R. We can't change those, 
right? But suppose we now decide that our CoA should have two different 
income accounts Y and Z instead of that one, transaction 1-5 going into 
Y and 6-10 going into Z.

We can do that be entering two  transactions to do the "correction". 
Since we probably want to retain the information about the original 
transactions most likely both transactions would be splits (for example, 
a single amount for what we are moving from X split five ways with the 
amounts being what the original transactions were but all going to Y). 
Here is where the old fashioned way which allowed essentially unlimited 
space to write in an explanation of what was going on useful.

Michael D Novack

PS: I do not understand the references to payments in this discussion. 
This is the accrual system, so income is connected to A/R before any 
payment received. The eventual payment (or not) is a transfer between 
A/R and cash (if a payment) or A/R and the bad debt expense (if written off)