why do i have duplicate contacts on my iPhone ios13

Duplicate contacts on your iPhone can occur as the result of using iCloud.

In rare instances, your contacts may be duplicated within iCloud due to an issue with the service itself. This is the worst case scenario, because it cannot be resolved without assistance. Check to see if you have duplicate iCloud contacts by signing in to the iCloud website. If you have duplicate contacts, and you cannot determine the cause, contact Apple Support to resolve the issue.

Do you have any other email accounts on your phone? If you do go to Settings/Passwords & Accounts and tap on each account. Make sure Contacts are off for all of them except the iCloud account. If that is not the source of the duplicates, and you are sure you don’t have duplicates in iCloud by logging in to https://icloud.com and clicking on Contacts, then do the following:

• On the phone go to Settings/[your name]/iCloud
• Turn off Contacts. When you are asked if you want to keep them on the phone, say NO and wait for it to finish cleaning up. This may take a few minutes.
• Just to be extra careful, restart your phone—>Restart your iPhone - Apple Support
• Then go to Settings/[your name]/iCloud again and turn on the Contacts switch. This should sync the contacts from iCloud to your phone.

Do you see the duplicates in iCloud? If you don’t the most likely reason is you have more than one email account on your phone and you chose to sync the contacts from two or more email accounts, and you have duplicates.

If all of the contacts are iCloud and if you have a Mac open the Contacts app on the Mac, then go to the Contacts menu and choose Look for Duplicates...

Great, glad it’s resolved.