Here are some tips to help you make the most of the features of nBill.

Front-end invoice and order lists:

You can make your lists of invoices and orders in your website front-end look a bit nicer by specifying styles in your template's CSS file.  Templates are supposed to have these settings already, but many don't.  You need style attributes for the following classes:  sectiontableheader, sectiontableentry1, sectiontableentry2.  The first one (sectiontableheader) defines how the title row will appear, and sectiontableentry1 and 2 define how alternate rows will look.

For example, if your template were predominantly green, you might want to use something like this in your template_css.css file:

.sectiontableheader
{
    font-weight:bold;
    background-color:#197b30;
    color: #ffffff;
}
.sectiontableentry1
{
    background-color:#ffffff;
}
.sectiontableentry2
{
    background-color:#ddeedd;
}

Changing the look of your invoices:

Invoices are template-driven, so a PHP developer can create a new template based on the existing one.  See this page for more details. 

Offering product upgrades:

If your product records relate to services that can be upgraded, this can present a problem because most payment service providers will not allow you to change the amount of a recurring payment via a script.  There are 2 ways of approaching this in nBill:

1) Create a new product for the upgrade, and set the price of it to the difference between the 2 products.  You can specify the lower priced product as a pre-requisite product on the order form for the upgrade.  Advantages: You can process the payment online as for any other product without any intervention on your part.  Disadvantages: The customer now has 2 recurring payments for different amounts which fall on different dates. If/when the customer decides to cancel their subscription, and if you want to refund any unused credit, you will have to calculate how much of each subscription is outstanding.

2) Manually alter the order record in nBill, optionally issuing a one-off invoice for the extra amount due between the date of the upgrade and the next billing cycle. If payments are made automatically using an online payment service provider, you will need to cancel the original payment schedule and set up a new one.

Method 1 is probably most suitable for payments which recur on a monthly basis (or more frequently), but method 2 is probably better for annual payments, especially if the customer pays by standing order or cheque.

Re-generating an Invoice:

If you generate an invoice for an order, then decide that you want to make an adjustment and re-generate the invoice, first consider just manually altering the invoice and/or order record. Otherwise, to re-do an invoice generation (assuming no further invoices have been generated in the meantime), first delete the old invoice record, then go into the vendor record and reset the 'next invoice number' to the previous number.  Go to the order record, and reset the 'next due date' to either today's date, or a date in the past.  You can then go ahead and generate the invoice again.