Set up Reminders accounts on iPhone
If you use the Reminders app with different accounts (such as iCloud, Microsoft Exchange, Google, or Yahoo), you can manage all your to-do lists in one place. Your reminders stay up to date on all your devices that use the same accounts.
Add your reminders stored in iCloud
Go to Settings > [your name] > iCloud > Show All, then turn on Reminders.
Your reminders stored in iCloud—and any changes you make to them—appear on your iPhone, iPad, Apple Watch, and Mac where you’re signed in with the same Apple ID.
Upgrade your reminders stored in iCloud
If you’ve been using Reminders with iOS 12 or earlier, you may need to upgrade your reminders stored in iCloud to use features such as attachments, flags, list colors and icons, and more.
Go to Settings
> [your name] > iCloud > Show All, then make sure Reminders is turned on.
Open the Reminders app.
On the Welcome to Reminders screen, choose one of the following options:
Upgrade Now: Begin the upgrade process.
Upgrade Later: A blue Upgrade button appears above your lists; tap it when you’re ready to upgrade your reminders.
Note: Upgraded reminders aren’t backward compatible with the Reminders app in earlier versions of iOS and macOS. See the Apple Support article Upgrading the Reminders app in iOS 13 or later.
Add other Reminders accounts
You can use the Reminders app to manage your reminders from other accounts, such as Microsoft Exchange, Google, and Yahoo.
Go to Settings
> Reminders > Accounts > Add Account.
Do any of the following:
Choose an account provider, then sign in to your account.
If your account provider isn’t listed, tap Other, tap Add CalDAV Account, then enter your server and account information.
Note: Some Reminders features described in this guide aren’t available in accounts from other providers.
To stop using an account, go to Settings > Reminders > Accounts, tap the account, then turn off Reminders. Reminders from the account no longer appear on your iPhone.