If the bill is showing as currently outstanding in the ledger, check if the there is also another, contra posting also outstanding, such as a receipt or credit note.
They may not have originally been allocated to the bill.
If that is the case, posting a BRO for 0.00 and allocating against the receipt or credit note and the bill will clear the outstanding postings.
If there are no unallocated receipts or credits to match against the bill, check the receipts allocated to the bill.
Double-click the posting to bring up the Posting Enquiry window and select the Allocate tab. In the top section will be the SIB details of the SIB that the receipt was allocated to.
The section below that should contain the details of what was allocated, i.e. the Fees/WIP and disbursements. If this section is empty, there is an issue with the allocation.
If this is the case then reverse the TCO/BRO that this has happened on and re-post making sure that the secondary allocation has correctly taken the value off.
If this doesn't rectify the issue please raise a new case online and reference the title of this article if this is the case.