Receivables
1. Why does the Age trial Balance when printed as aged as of and calculated as at gives different report.
I am printing now for a prior period.

Which report is linked to the general ledger.

2. Inventory Clearing/ Purchases ? Receipts account.
This account holds purchase invoices, costs related to purchases and inventory receipts.

What could cause this to be in a credit balance and how can this be corrected.

The Aged Trial Balance should tie to the AR control account when printed "Calculated as of" the period ending date. "Calculated as of" ignores transactions entered after the date selected. "Aged as of" includes all the transactions on file.

You'll likely have to inspect the transactions that are being sent to the Clearing account to see where the problem lies. One of your other accounts PO/Inventory accounts may be "pointing" at this GL account.