Why is my discount code field missing on my mobile checkout page?

The discount code field is usually hidden on mobile due to restrictive CSS viewport rules that push checkout elements off-screen, or Shopify theme settings that tuck the field behind an un-expanded order summary accordion.

“This tends to crop up when your mobile CSS pushes the field off-screen, or it’s tucked behind a collapsed order summary nobody thinks to expand. I’ll dig in, get it visible again within 24 hours, and it’s just $99.”
— Jeff Bollettino, Managing Director, Ignite Conversions