Can someone give me some information on the correct procedure for a receivable that was posted to the wrong customer approximatelty 6 months ago. I need to reverse that and apply to correct custimer !!

Was this an incorrectly posted invoice or cash receipt?

For a cash receipt, here's the link on this forum to the question you previously asked on June 26th.

If it is an incorrect invoice, you should post a credit note or adjustment against the invoice - with the same transaction date so that the accounting is reversed for the correct fiscal period - and re-enter the invoice for the correct customer.