Field Business Area to be made default

Dear Expert,

In our system, we have made the business area field mandatory for vendor invoice, it is made in OB41 for posting key 31. Now we are developing the process in "REFX" for reverse lease, where in we will be posting the vendor invoices for lease rent paid  through REFX.

While running this process, we are getting an error for "Business Area" field not filled in . We use Business Area only for information purpose and no splitting is done at  Business Area level.

Now how can I, make the Business area field default, as there will be only one business area for the company code, under which the REFX transaction is getting posted.

Kindly advise.

Regards

Shailesh