NEW YORK (AP) — Starbucks will soon let customers leave tips with its mobile payment app, which raises the question — how often do people tip their baristas?

The coffee chain says the mobile tipping option, which it announced more than a year ago, will be available on its updated app for iPhones starting March 19. The rollout comes as the company’s app has surged in popularity, with roughly one out of every 10 purchases now made with a mobile device.