The Notes app on iPhone, iPad and iPod Touch devices lets you create interactive checklists. To create a Checklist on iPhone running iOS 9 or later, do as follows:
1. Open the Notes application on your iOS device
2. Tap the Create New Note button on the bottom right
3. Tap the Add button on the bottom right (since the keyword is visible, look for it in the row over the keyboard layout)
4. Tap the Checklist button (it's a mark icon with a circle around it)
5. And start to create a checklist on iPhone
6. Tap Done when you are finished, and since it's an interactive note on your iPhone, you may check the items or un-check them.