In Google Ads: Conversion lag (also known as "conversion delay") refers to the delay when people click an ad and when they perform a specific conversion action (for example with, install, purchase, add-to-cart, etc.). Because Google Ads reports conversions by query date, you may not always see the most updated conversion numbers. They can sometimes cause CPA to look inflated and ROAS to look deflated.
Campaign types eligible for conversion lag reporting
App campaigns for install
App campaigns for engagement
Search campaigns