You may or may not know it but at the start of April, Google has allowed users in Canada as well as Australia, France, Germany, Japan, and the UK input their payment and delivery information in Google Assistant settings. Through this feature you can add your payment method (credit or debit card) as well as shipping address. These payment profiles can be used to pay for items and services of third-party services that have implemented the feature. Just head to the Payments menu in your Google Assistant settings to input your information.
Source: Android Police