Before I start with this post, I want to emphasize once again, in all my examples I use W1 database. I know that prepayments can be quite differently from country to country, but I have used only W1 examples here.

Now, when this is clear, we can continue with examples. First, I will describe purchase prepayment invoice. When we choose to create Prepayment Invoice from Purchase order, system will post document with G/L Account in line (from General Posting Setup) and with following G/L entries:

The similar situation is when we create and post sales prepayment invoice. Then, we will get these G/L entries:

If we want to post Prepayment Credit Memo, in both cases, we will get the same entries, but with opposite signs.