There are a few different areas on the Client Matter Enquiries you can check to see what has happened with the postings:
If you have an Anticipated billed to pay balance included in your office balance then you need to check what AD's have been posted and not paid out by looking at all disbursements and adding the column in Amount Paid. This field will show you what needs paying and then add in Amount Billed this will then show you what has been billed.
If you have an office balance but no Anticipated balance and the bills don't match that value it could be that either you have an Unallocated Receipt/Credit note (add this field via the Configure Matter Detail) this will need allocating to a bill or reversing if this is incorrectly showing and not the same figure as the bill. There could also be a TOC posting that is affecting the balance and is showing in the disbursements.
If you have balances on a report and the bills/disbursements were paid off before that date, check to make sure the postings were not backdated and are in a different financial year and period to when these reports are run.