Allow Account Entry is an option in Account Maintenance screen. Account Maintenance is used to maintain (create) the Posting account. Allow Account entry is marked by default in the Account Maintenance screen.
When it is unmarked, It prevents an user from manually entering or choosing this account in transaction or distribution entry windows irrespective of the module. However, this account can be used as the default posting account.
This feature works well with accounts like Inventory, Accounts Payable, Accounts Receivable which minimize balances mismatch between subsidiary ledgers and General ledger as it does not allow direct posting into GL.
There is an exception to this feature. This functionality fails to work in Purchase order entry. In Purchasing Item detail entry, this account can be selected manually despite the selection in Account Maintenance. This might be a possible bug.