You may change the account for unposted documents.

Sales documents - Select a different debtor (customer / client) account for unposted sales documents (i.e. Invoices, Credit notes or Quotes). 

Purchase documents - Select a different creditor (supplier / vendor) account for unposted purchase documents (i.e. Purchases, Supplier returns or Orders).  

Change a debtor (customer / client) account

To change a debtor (customer / client) account for a unposted document:

  1. Select the Invoices, Credit notes or Quotes document type.
  2. Select the document to change the account for.
  3. Right-click and select Documents → Change account option on the context menu. The "Debtor accounts" list screen will list only the active debtor (customer / client) accounts:

  1. Select a different account. 
  2. Click on the Open or OK button.  

Change the creditor (creditor / vendor) account

To change the creditor (creditor / vendor) account for a unposted purchase document:

  1. Select the Purchases, Supplier returns or Orders document type.
  2. Select the document to change the account for.
  3. Right-click and select Documents → Change account option on the context menu. The "Creditor accounts" list screen will list only the active creditor (supplier / vendor) accounts:

  1. Select a different account. 
  2. Click on the Open or OK button.