Paul Ovigele, Ovigele Consulting
When purchase orders are entered in the standard SAP system, the general ledger account that is posted to is derived in the below ways:
(1) If it is a purchase of inventory (stock), then the general ledger account assigned to the valuation class that is linked to the material is defaulted;
(2) If it is the purchase of a fixed asset, then the general ledger account that is assigned to the account determination that is linked to the asset class that the asset belongs to is defaulted;
(3) If you are not purchasing fixed assets or inventory, then the system will use the ‘Account Modification’ that is assigned to the ‘Account Assignment Category’ which is specified in the purchase order. This Account Modification is linked to a general ledger account in the account determination table (transaction OBYC). In this transaction, if you double-click on transaction key GBB and look at the relevant Account Modification (called “General Modification” in this table), it is the general ledger account that does not have a valuation class assigned to it that will be defaulted in the purchase order.
(4) If you are not purchasing fixed assets or inventory but you do not want just one general ledger account to be defaulted for all purchase orders that use that account assignment category, then you can assign material groups (which are specified in the purchase order) to valuation classes, and in turn assign the valuation classes to general ledger accounts. You can find out more about this option in Part 7 (Tip 69) of my book “100 Things You Should Know About Financial Accounting”
If you have scenarios that do not fit into the options described above (and you do not use “feed in” systems into SAP ERP, such as EBP, CRM or an external system to create your purchase orders) then it is most likely that the folks in the purchasing department are entering the general ledger accounts manually in the purchase orders. No matter how well-defined your general ledger account descriptions are, they are still probably confusing to people in non-accounting departments, and hence it is very easy for them to enter the wrong accounts when making non-stock purchases.
My general recommendation to the above issue is to use options 3 or 4 above; however, if you simply want to restrict certain accounts (such as payroll) from being entered into POs then you can set the field status group of the G/L accounts to be incompatible with the account assignment categories used in the purchase orders.
For example if you are using account assignment category K (Cost Center), you can go to transaction OME9, double click on this account assignment category and make the field “Functional Area” an optional entry. You can then go to transaction FS00 for the G/L account (that you do not want to be posted on a purchase order), go to the “Create/bank/interest” tab and note the relevant ‘Field Status Group’; then go to transaction OBC4 and for the relevant Field Status Variant, double-click on the field status group that the G/L account is assigned to and double-click on “Additional Account Assignment” and set the Functional Area field to “Hidden”.
Once this is done, though a purchase order can be entered with account assignment category “K” and the above G/L account, the system will issue an error message when you save the purchase order because of the conflicting field statuses of the account assignment category and G/L account.
For more information on how to optimize your SAP Financials landscape, I've put together my top tips in the book 100 Things You Should Know About Financial Accounting with SAP which is published by SAP Press.