In many ways bills are the opposite of invoices as they allow you to track the payments you make to your suppliers.
Bills cover anything you buy for the business but don't need to pay for straightaway. A good example would be work farmed out to a sub-contractor that doesn't get settled until 30 days after an invoice has been received from the supplier.
If you're unsure whether to record a particular business cost as a bill, an expense or a bank payment, take a look at this article for more information.
Adding a bill means you can keep track of who you owe, and when they're expecting payment.
When you create a bill you can enter both a Bill Date and a Due Date, assign it to a Contact and specify the Type (like you would with Expenses or Bank Entries).
Bills can also have attachments - handy for storing those scanned or PDF versions of the originals.
Of course, bills are comprehensively handled by our accounting engine, including the sales tax and, for our UK users, all the various rates of VAT.