Ensure you click Edit to make changes and 
Update to save them
Click Customer screen > Account Details tab
Account Details
Account Code
By default the system will generate a new customer reference number and use this as the customer account number. If you export data to an accounts package this account code must match to the same customer(s) in the accounts software. See Sage link below.
Payment Terms
This is a selection list drop down box. Click Edit Popup Contents 
to add a new entry.
Nominal Code
This will be completed with your default nominal code (set in system configuration) but it can be changed by over-typing it here.
On Stop
Tick this box to record the customer as "on stop", e.g. they have unsettled outstanding balances. The customer's details appear shaded red on the customer screen and the projects screen so you can easily see the customer is not active.
Settlement Discounts
This must be enabled in system configuration otherwise the sub-heading and the following options are not displayed. When enabled you can set terms that if a customer pays in X days they receive an extra discount.
Discount
Set a discount percentage for a blanket settlement discount
Days
Set a number of days in which the settlement discount applies
Catalogue Settlements
Click the button to add entries for each catalogue. This allows you to set a settlement discount which applies only to one catalogue. Each catalogue can have their own settlement terms.
Discount Bands
Here you can set a band (or group) of discounts. One band of discounts can be applied easily to multiple customers. E.g. a staff discount can be setup as a band and then chosen when needed.
Click Edit Popup Contents to add and configure a new band. See Discount Bands topic.
Customer Specific Discounts/Prices
Product Discount
Enter a percentage to be removed from each product price on this customer's order.
Order Discount 1
Enter a percentage to discount the total order value
Order Discount 2
Enter a percentage to give an additional discount on the total order value
Click the following 3 buttons to open their settings:
Click the button to open a window to enter catalogue discounts. The selected customer can receive a specific discount on a catalogue.
Click the button to open a window to enter specific product discounts. The selected customer can receive a special price on specific products.
Click the button to open a window to enter specific discounts and/or margins for a supplier, for the selected customer. Discounts set here override the system-wide discounts and margins.
If you need to specify more than 1 type of discount you need to know the order in which they are applied. There is a hierarchy where one discount overrides the other.
The order goes from least specific to most specific:
•Product Discount •Discount Band •Catalogue Discount •Product Prices |