Reallocate button in F110

Dear All,

I have update the vendor master via FK02. I have also configured all the details in FBZP. Similarly When posting an invoice in FB60 I have also mentioned the house bank.

Now my question is when running F110 , (Edit Proposal) , there is a reallocate button. If I didn't mention anything on that reallocate button then system is not posting the payment document.

When I have already done all the configuration then what is the necessity to put values again on reallocate button. (on reallocate the system is picking the payment method and house bank, but not the account id) Why.

Similarly how the system will make payment against ranking of banks against putting house banks in either invoice or reallocate button . Please guide.

Regrds

Soumya.