To write a review for a purchase made directly on Google, check your email for an invitation to review your shopping experience with the seller as well as for individual products you purchased.

If you make a purchase on a non-Google shopping site you may see an invitation to write shopping reviews via the Google Customer Reviews program. 

If you opt-in to being contacted by Google you will receive an email to write a review within a few days of the estimated delivery date of your order.

You can also search for the product on Google Search. Under "Reviews", you can add a star rating and enter your review. 

Learn more about reviews on Google Search.