A GL account can be designated as a control account in order to post only transactions created by the subledgers specified, to the account. This is normally done to help ensure that the subledger remains in balance with its related GL account. General Ledger checks for this by looking at the first two characters of the source code included with each subledger transaction. These first two characters must match the subledger codes designated for the control account.
As an example, let's make the AP Trade account in the GL a control account for the subledger AP.
When I refer to the AP Trade account, I am referring to the account that is designated in AP Setup / Account Sets as the Payables Control account.
In GL Accounts, on the Detail tab, there is an option for ‘Control Account’. Once this option is selected, a new tab appears called ‘Subledger’. Only journal entries coming from sub-ledgers that are identified on this tab will be able to post into the GL. So, in order to keep the AP in balance to the GL, we only want the AP subledger to show up on this tab.
What this does is stop any entries from any other module besides AP from being posted into the AP control account. If the entry comes from any other sub-ledger, the entry will not post in the GL and will be kicked out into an error batch. If the entry to the control account is being entered through the GL, an error message will be seen immediately upon selecting that account in the JE: