Just found this link that shows all available Amazon Vouchers.
https://www.amazon.com/Coupons/b?ie=UTF8&node=2231352011 - amazon.com
https://www.amazon.co.uk/b?ie=UTF8&node=10372583031 - amazon.co.uk
Sign in and Save them to your account so they can be applied during checkout.
Various deals across a broad range of products such as:
30% off pet food
25% off chocolates
20% off beer
Note: Amazon.co.uk link will not work on mobile devices. Enable desktop version through your browser or use a PC/Laptop.
If a product has a voucher available it displays it clearly below the price. You do not need to consult this page if you were going to buy a product but thought 'oh I wonder if there is a voucher for this'. But you need to first click on the voucher landing page to activate the ability to see & use available vouchers on eligible products. These vouchers are immediate discounts off the advertised price and are independent of any credit that you may have.