Documentation

Item Price Book Maintenance
This is to maintain item pricing by Price Category, Debtor or Creditor.
Go to Stock > More Stock Maintenance > Item Price Book Maintenance

Tick the checkbox - Select Item code and UOM.
Press Edit.

All Debtor will list out at here.

Key in the special selling price into fixed price column. Press OK.

OR
Tick the checkbox Item Code, UOM and select it.
Tick the checkbox - Debtor, select ONE Debtor only that u want to set the special price.
Press Edit button.

Here will just show one debtor only that u selected.

Key in the special selling price into fixed price column. Press OK.

After setup Item Price Book by Debtor 300-Y001,
When users create a new transaction, select debtor, the Item Price will follow Item Price Book.

The debtor that not set any item Price book setup,
The unit price will follow the Item Standard Selling Price (Item > Details > UOM Details)