Download and install the custom Purchase Order with Account Number template. It is compatible with RMS version 1.2.
To add this PO template to RMS:

1.    Close all applications on the workstation
2.    Download poaccountnumber.exe. This is a self-extracting zip file containing the Purchase Order with Account Number template.
3.    Double-click the downloaded file and click Unzip.
Note: The file is extracted to the default installation directory for RMS receipt templates (C:\Program Files\Microsoft Retail Management System\Store). If this is not the installed location, click Browse and select the RMS Receipt Templates directory, then click Unzip.
4.    If prompted to overwrite an existing file, click Yes
5.    Once the file is extracted, open Store Operations Administrator
6.    Select the File, Configuration from the menu bar
7.    Select the Templates tab and click browse next to the Purchase Order field 
8.    Select the file poaccountnumber.xml file and click Open, OK
9.    Exit Store Operations Administrator
10.    Open Store Operations Manager. All purchase order will now use this template when previewing or printing. The Account Number will appear at the top of the field in the To area.