====== Account Balances ======
The account balance is updated every time an invoice, credit note or payment receipt is added to a customer's account.  


===== How are the aged balances calculated? =====
The aged balances are running balances on the customer account.  They are not related to the reconciliation process therefore, in general //the age balance for a given month will not be the total of all the sales for that month//.

The following invariant is always true for any set of balances:

''Total = the sum of all the aged balances''


For the purpose of the examples on this section we will create an account with current
balance of:
||        | Total    | May     | April   | March   | February | Over Due ||
|| Before |  1500.00 |  100.00 |  200.00 |  300.00 |   400.00 |   500.00 ||

==== Invoices ===
All invoices are add to the current month.

** Example **
An invoice is raised for 150.00.

||        | Total    | May     | April   | March   | February | Over Due ||
|| Before |  1500.00 |  100.00 |  200.00 |  300.00 |   400.00 |   500.00 ||
|| After  |  1650.00 |  250.00 |  200.00 |  300.00 |   400.00 |   500.00 ||

The value of the invoice was added to the ''Total'' and ''May''.

==== Credit Notes ===
All credit notes are add to the current month.

** Example **
A credit note is raised for 175.00.

||        | Total    | May     | April   | March   | February | Over Due ||
|| Before |  1500.00 |  100.00 |  200.00 |  300.00 |   400.00 |   500.00 ||
|| After  |  1300.00 |  -75.00 |  200.00 |  300.00 |   400.00 |   500.00 ||

The value of the credit deducted from to the ''Total'' and ''May''.

==== Receipts ===
All receipts are deducted from the oldest balance. 
If the aged balance would become negative, the difference is carried to the next younger balance.

** Example 1, basic.**
A receipt is raised for 300.00. 

||        | Total    | May     | April   | March   | February | Over Due ||
|| Before |  1500.00 |  100.00 |  200.00 |  300.00 |   400.00 |   500.00 ||
|| After  |  1200.00 |  100.00 |  200.00 |  300.00 |   400.00 |   200.00 ||

The value of the receipt is deducted from the ''Total'' and ''Over Due''.

** Example 2, roll over.**
A receipt is raised for 1000.00. 

||        | Total    | May     | April   | March   | February | Over Due ||
|| Before |  1500.00 |  100.00 |  200.00 |  300.00 |   400.00 |   500.00 ||
|| After  |   500.00 |  100.00 |  200.00 |  200.00 |     0.00 |     0.00 ||

The value of the receipt is deducted from the ''Total'', ''February'' and ''Over Due'' are zeroed and the remainder is deducted from ''March''.

** Example 3, a bounced cheque or reversal of a receipt.**
A receipt is raised for 800.00.  

||        | Total    | May     | April   | March   | February | Over Due ||
|| Before |  1500.00 |  100.00 |  200.00 |  300.00 |   400.00 |   500.00 ||
|| After  |   700.00 |  100.00 |  200.00 |  200.00 |   200.00 |     0.00 ||

The value of the receipt is deducted from the ''Total'', ''Over Due'' is zeroed and the remainder is deducted from ''February''.

A receipt is raised for //-800.00//.  

||        | Total    | May     | April   | March   | February | Over Due ||
|| Before |   700.00 |  100.00 |  200.00 |  200.00 |   200.00 |     0.00 ||
|| After  |  1500.00 |  100.00 |  200.00 |  200.00 |   200.00 |   800.00 ||

The value of the receipt of ''-800.00'' is "deducted" from the ''Total'' and ''Over Due''.

** Example 4, A credit not is raised, and a refund issued. **
A credit note is raised for 150.00.  

||        | Total    | May     | April   | March   | February | Over Due ||
|| Before |  1500.00 |  100.00 |  200.00 |  300.00 |   400.00 |   500.00 ||
|| After  |  1250.00 |  -50.00 |  200.00 |  300.00 |   400.00 |   500.00 ||

The value of the credit was deducted from the ''Total'' and ''May''.

A receipt is raised for //-150.00//.  
||        | Total    | May     | April   | March   | February | Over Due ||
|| Before |  1300.00 |  -50.00 |  200.00 |  300.00 |   400.00 |   500.00 ||
|| After  |  1500.00 |  -50.00 |  200.00 |  300.00 |   400.00 |   650.00 ||

The value of the receipt of ''-150.00'' is "deducted" from the ''Total'' and ''Over Due''.