Customer netting off

Hi,

We have a net off between the customer for invoices.

Say customer A and Customer B.In customer A master record customer B is maintained as rebate recipient

partner function tab.

when we run AR proposal say for Customer A it picks the invoice,but when we run AP proposal say for customer B its not picking any invoices.

Can some one please let me know the concept and configuration behind this.

I say it again its net off between customer by running proposal through F110.

Thanks,