Reminders won't sync with iMac

I have had an iMac for a while and recently bought an iPhone 5S.

I have managed to get Photos and Calendar to sync OK between them, but can't find any way to get Reminders to sync.

I have set up a Reminder on the Mac but nothing appears on the iPhone. As far as I can see everything is properly enabled on both sides and in iCloud.

What am I not doing or doing wrong?