Teachers get asked this in evaluations, PD sessions, and grad school classes: is an exit ticket formal or informal assessment? The honest answer is that it depends on how you use it.
The simple difference
Informal formative assessment is quick and unplanned or loosely planned: thumbs up, a show of hands, listening in on group talk, a quick question at the door.
Formal formative assessment is planned and recorded: a written check with the same questions for everyone, collected and looked at, with results you write down.
Neither one is graded for a score. Both are about adjusting your teaching.
Where exit tickets fall
A planned exit ticket with a specific question, collected from every student and sorted afterward, is formal formative assessment. A quick "tell me one thing you learned on your way out" is informal.
Both are useful. The difference is what you can do with the results.
Why it matters
If you need evidence for a data meeting, an evaluation, or an intervention plan, formal exit tickets give you a record. Sort them into three piles (got it, almost, not yet) and jot down the numbers. That takes about five minutes and gives you real data.
If you just need a pulse check before tomorrow's lesson, informal works fine and saves paper.
A good mix
Use informal checks all period long. Use a formal exit ticket two or three times a week, especially before a quiz or at the end of a big idea.
Free tools
Formal vs Informal Formative Assessment on Elevate the Norm goes into more detail.
What to Do With Exit Ticket Answers the Next Day shows the three-pile sort.
What Is an Exit Ticket? is a quick refresher if you're new to them.
Want it ready to print
Everything above is free. If you'd rather skip the prep, my TPT store, Teacher Emergency Toolkit, has print-ready packs for grades 6–12, including a free resources shelf and teacher forms and templates.
Need a warm-up for tomorrow? A new set of free bell ringers goes up every morning at Daily Bell Ringers.