# Donations and Invoice Payments
Products can be configured to have a customer entered price - instead of a fixed price, a price entry field is displayed instead.
To configure a product this way, check the Allow customer to enter price option on the Overview tab when editing a product. When this is checked, the product's options will adjust. The follow fields appear:
- Default Price
- Price Suggestions
- Minimum Price
- Maximum Price
Use these fields to control the limits of what can be used as a payment value. Also set the Offer quantity selection option to No, only allow one of this product in the cart.
Invoice Payments
If you are configuring a product to be used for customers to pay existing invoices online, add a Text Field option to the product, set to be required, with a label such as 'Invoice Number'. This field can be used to associate the payment with an invoice number, and also allows multiple invoice payments to be made within the same order.