There are a number of reasons why this may happen.

One reason may be due to journals posted to the debtors control account. If a journal is posted to the debtors control account, it changes the value on the nominal code. However, the same value is not reflected anywhere in the customer's record, and as a result does not affect the aged debtors reports, resulting in the discrepancy.

Under normal circumstances, you should not post journals to the debtors control account. The only time this should happen is when entering and reversing opening balances.

1. Click Nominal codes then click Reports.
2. Click Day books then click Day Books: Nominal Ledger.
3. Complete the Criteria as follows:
   • Transaction Date: Select Between (inclusive) then enter 01/01/1980 and the last day of the month being reconciled.
   • Nominal code: Select Is then enter 1100 Debtors Control.
4. Click OK then check the total amounts in the Debit and Credit columns.
   
   If these values are the same then journals aren't the reason for the difference. If the values are different, subtract one from the other to give the difference.