Google steadily introduces enhancements to Shopping ads, and before you can execute, you have to know how to choose the right approach.
When product prices are discounted during a sale, there are 2 common options that websites will utilize to communicate the price cut. Taking a look at the product landing page can typically clue you in on what to do next to ensure that your ads effectively promote this offer.
Discount Shown on Landing Page?
Sale Price Annotations / Badge
When the price discount is shown on the landing page, you will need to pass the original and sale price values over to Google in the product data feed for the Sale Price Annotation & Badge to appear on the ad.
Discount Shown in the Shopping Cart?
Merchant Promotion
When the eligible price discount can only be seen when added to the Shopping Cart, you will need to leverage Google's Merchant Promotions. Check Eligibility Requirements.
Summary
Google continues to expand upon these and test new things in this area but knowing the fundamentals on which direction to go will help ensure your ad gets the attention it is eligible for.