You add a reminder on your iPhone while running errands, expecting it to pop up on your Mac when you get home. But it never shows up. Your Mac and iPhone seem to be living separate lives, and your to-do lists are a mess because of it.
This sync problem is surprisingly common, and the good news is that it usually has a simple fix. In this post, you will learn exactly why your reminders stop syncing between your Apple devices and how to get everything working together again.
What Does It Mean When Reminders Stop Syncing?
When your reminders sync properly, anything you add, edit, or delete on one device shows up on all your other Apple devices almost instantly. Your iPhone talks to iCloud, iCloud talks to your Mac, and everyone stays on the same page. It feels seamless, like magic.
But when syncing breaks, that communication chain snaps somewhere along the line. You might add a grocery list item on your phone and wait hours for it to appear on your Mac. Or you might check off a task on your computer, only to find it still sitting unchecked on your phone later that day.
The problem can show up in different ways:
- One-way sync failure: Changes on one device update to the other, but not the other way around.
- Complete sync failure: Neither device reflects changes made on the other.
- Delayed sync: Updates eventually appear, but it takes hours or even days instead of seconds.
- Missing reminders: Some reminders vanish entirely from one device.
Leaving this unfixed creates real headaches. You might miss important tasks because they never appeared where you expected them. Or you could end up with duplicate entries after manually adding things twice. Over time, you lose trust in the system entirely and stop relying on it, which defeats the whole purpose of having a digital reminder tool.
Reminders Not Syncing Between iPhone and Mac: Likely Causes
Before jumping into fixes, it helps to understand what might be causing the problem. Once you know the root cause, the solution often becomes obvious.
1. iCloud Sync for Reminders Is Turned Off
This is the most basic reason, and it trips up a lot of people. iCloud handles the behind-the-scenes work of keeping your reminders matched across devices. If Reminders is switched off in your iCloud settings on either your iPhone or your Mac, sync simply will not happen.
Sometimes this setting gets toggled off by accident. Other times, people turn it off intentionally during troubleshooting for a different issue and forget to turn it back on.
2. You Are Using Different Apple IDs
Your Apple ID is like a key that unlocks your personal iCloud data. If your iPhone is signed into one Apple ID and your Mac is signed into a different one, they are looking at two completely separate sets of reminders.
This happens more often than you would think. Maybe you created a new Apple ID at some point and forgot to update all your devices. Or perhaps a family member set up one of your devices using their account.
Even a small typo in the email address can mean you are signed into the wrong account without realizing it.
3. Weak or Missing Internet Connection
iCloud needs the internet to sync your data. If your iPhone is on a spotty cellular connection or your Mac is disconnected from Wi-Fi, your reminders have no way to travel between devices.
The tricky part is that your device might look connected but actually have very limited data flow. A weak signal or a congested network can slow things down so much that sync appears broken.
4. Outdated Software
Apple regularly updates iOS and macOS to fix bugs and improve how features work. If your iPhone or Mac is running old software, it might have a glitch that interferes with iCloud sync.
Older software versions sometimes struggle to communicate properly with Apple’s servers. An update that came out months ago might contain a fix for the exact sync problem you are experiencing.
5. iCloud Storage Is Full
Your iCloud account comes with a limited amount of storage space. When that space fills up, iCloud stops accepting new data. This means new reminders or changes to existing ones cannot upload to the cloud.
Your devices might not give you an obvious warning about this. You could be over your limit without even knowing it, and sync quietly fails in the background.
Reminders Not Syncing Between iPhone and Mac: How to Fix
Now that you know what might be causing the issue, let’s walk through the fixes. Start from the top and work your way down until your reminders start syncing again.
1. Make Sure Reminders Is Enabled in iCloud
This is the first thing to check on both devices. If this setting is off, nothing else matters.
On your iPhone:
- Open the Settings app
- Tap your name at the very top of the screen
- Tap iCloud
- Look for Reminders in the list and make sure the toggle is green (on)
On your Mac:
- Click the Apple menu in the top left corner
- Select System Settings (or System Preferences on older versions)
- Click your name or Apple ID
- Click iCloud
- Find Reminders and check the box next to it
After enabling it on both devices, give it a few minutes. Open the Reminders app on each device and see if your lists match up now.
2. Confirm You Are Using the Same Apple ID
Both devices need to be signed into the identical Apple ID for sync to work. Here is how to check.
On your iPhone: Go to Settings and tap your name at the top. Your Apple ID email appears right below your name.
On your Mac: Open System Settings, click your name, and look at the email shown there.
If the emails do not match exactly, you have found your problem. Sign out of the incorrect account and sign back in with the right one. Keep in mind that signing out and back in might temporarily remove some data from the device, but it will download again from iCloud once you sign in with the correct account.
3. Check Your Internet Connection
A quick test can tell you if connectivity is the issue. Try loading a webpage on both your iPhone and your Mac. If pages load slowly or not at all, your internet connection needs attention before sync can work.
On your iPhone, try switching from Wi-Fi to cellular data, or vice versa. On your Mac, move closer to your router or restart it entirely. Sometimes a fresh connection is all it takes.
Once you have a stable connection on both devices, open the Reminders app and create a test reminder. Watch to see if it appears on the other device within a minute or two.
4. Update Your Software
Running the latest software gives you the best chance at smooth syncing.
On your iPhone:
- Go to Settings
- Tap General
- Tap Software Update
- If an update is available, tap Download and Install
On your Mac:
- Click the Apple menu
- Select System Settings
- Click General, then Software Update
- Install any available updates
Updates can take a while, especially major ones. Let both devices finish updating and restart before testing sync again.
5. Force a Sync by Toggling iCloud Off and On
Sometimes iCloud needs a little push to start working again. Turning off Reminders in iCloud and then turning it back on can force a fresh sync.
Go to your iCloud settings on your iPhone and toggle Reminders off. A message might ask if you want to keep or delete the reminders on your device. Choose to keep them. Wait about 30 seconds, then toggle Reminders back on.
Repeat this process on your Mac. After re-enabling Reminders on both devices, open the app and check if everything matches. This simple reset clears out small glitches that can block sync.
6. Check Your iCloud Storage
If your storage is full, you need to free up space or buy more.
On your iPhone: Go to Settings, tap your name, tap iCloud, and look at the storage bar at the top. It shows how much space you have used and how much is left.
On your Mac: Open System Settings, click your name, click iCloud, and check the storage graph.
If you are at or near your limit, you have a few options. Delete old backups, photos, or files you no longer need. Or you can upgrade to a paid iCloud plan with more storage. Apple offers plans starting at a small monthly fee for extra gigabytes.
7. Contact Apple Support
If you have tried everything above and your reminders still refuse to sync, it might be time to call in the experts. Apple Support can look deeper into your account and devices to find problems that are not visible from the surface.
You can reach them through the Apple Support app on your iPhone, by visiting their website, or by making an appointment at an Apple Store. Sometimes a problem lies on Apple’s end, like a server issue, and only they can confirm and fix it.
Wrapping Up
Getting your reminders to sync between your iPhone and Mac usually comes down to a few key settings. Checking your iCloud options, making sure both devices use the same Apple ID, and keeping your software updated will solve the problem in most cases.
When these basics are in order, your devices will talk to each other smoothly again. Your to-do list will stay consistent no matter which screen you are looking at, and you can trust that nothing important slips through the cracks.