When you run the ``Aging'' process, *Qba* updates the
balances and applies service charges to delinquent clients.
*Qba* maintains the following balance ``buckets'':

**Net balance**- contains the up-to-date balance of a client. This bucket is automatically updated whenever an invoice item is processed and during aging if any service charges are applied. This bucket is equal to the sum of the Curr, 30, 60 and 90 buckets plus the difference of this month's payments and charges.
**Current balance**- gets populated with the ``Net balance'' total(less any 30/60/90 balances) when the aging process has run. It helps to think of the ``Current Balance'' bucket as a ``0 - 30 day balance bucket''. That is, this bucket remains equal to zero until the aging process is run for an account that has a positive net balance. After the aging process, the positive balance gets shifted to this ``Current balance'' bucket and the ``This month's payments'' and ``This month's charges'' get cleared. After the next month's aging process, if there is a positive balance in this ``Current balance'' bucket, the amount gets shifted to the ``30'' bucket, the ``30'' bucket amount gets shifted to the ``60'' bucket and so forth.
**``30''**- gets populated with the amount from the ``Current'' bucket during the aging process -- provided there is still a ``Net'' balance. Think of this bucket as holding amounts owed that are 30-60 days old.
**``60''**- contains balances that are 60-90 days old
**``90''**- contains balances that are 90+ days old.

Service charges are only applied to balances that are in the ``30'', ``60'' and ``90'' day buckets. If there is a month whereby a client's monthly payment is greater than the monthly charges, the difference is subtracted first from the older buckets first until the payment amount is exhausted. For example, suppose John has $50.00 in the 90-day bucket, $20.00 in the 60-day bucket, $13.50 in the 30-day bucket and $12.00 in the curr bucket. Further, assume at the end of the month John had no charges but made a payment of $60.00. The 90-day bucket will be set to $0.00 and then the 60-day bucket will be set to $10.00. Then after the aging process, the 60-day bucket value of $10.00 gets shifted to the 90-day bucket. The 30-day bucket of $13.50 gets shifted to the 60-day bucket. The ``curr'' bucket of $12.00 gets shifted into the 30-day bucket. The ``curr'' bucket gets set to $0.00 since there was a credit for this month.