diff --git a/apps/dav/lib/CardDAV/AddressBookImpl.php b/apps/dav/lib/CardDAV/AddressBookImpl.php
index 6ec3fed827..02dc7c5d01 100644
--- a/apps/dav/lib/CardDAV/AddressBookImpl.php
+++ b/apps/dav/lib/CardDAV/AddressBookImpl.php
@@ -281,12 +281,7 @@ class AddressBookImpl implements IAddressBook {
 			}
 		}
 
-		if (
-			$this->addressBookInfo['principaluri'] === 'principals/system/system' && (
-				$this->addressBookInfo['uri'] === 'system' ||
-				$this->addressBookInfo['{DAV:}displayname'] === $this->urlGenerator->getBaseUrl()
-			)
-		) {
+		if ($this->isSystemAddressBook()) {
 			$result['isLocalSystemBook'] = true;
 		}
 		return $result;
@@ -309,4 +304,26 @@ class AddressBookImpl implements IAddressBook {
 
 		return null;
 	}
+
+	/**
+	 * @inheritDoc
+	 */
+	public function isShared(): bool {
+		if (!isset($this->addressBookInfo['{http://owncloud.org/ns}owner-principal'])) {
+			return false;
+		}
+
+		return $this->addressBookInfo['principaluri']
+			!== $this->addressBookInfo['{http://owncloud.org/ns}owner-principal'];
+	}
+
+	/**
+	 * @inheritDoc
+	 */
+	public function isSystemAddressBook(): bool {
+		return $this->addressBookInfo['principaluri'] === 'principals/system/system' && (
+			$this->addressBookInfo['uri'] === 'system' ||
+			$this->addressBookInfo['{DAV:}displayname'] === $this->urlGenerator->getBaseUrl()
+		);
+	}
 }
diff --git a/apps/dav/tests/unit/CardDAV/AddressBookImplTest.php b/apps/dav/tests/unit/CardDAV/AddressBookImplTest.php
index cc7e50e937..242106fbcc 100644
--- a/apps/dav/tests/unit/CardDAV/AddressBookImplTest.php
+++ b/apps/dav/tests/unit/CardDAV/AddressBookImplTest.php
@@ -447,4 +447,63 @@ class AddressBookImplTest extends TestCase {
 			'isLocalSystemBook' => true,
 		], $array);
 	}
+
+	public function testIsSystemAddressBook(): void {
+		$addressBookInfo = [
+			'{http://owncloud.org/ns}owner-principal' => 'principals/system/system',
+			'principaluri' => 'principals/system/system',
+			'{DAV:}displayname' => 'display name',
+			'id' => 666,
+			'uri' => 'system',
+		];
+
+		$addressBookImpl = new AddressBookImpl(
+			$this->addressBook,
+			$addressBookInfo,
+			$this->backend,
+			$this->urlGenerator
+		);
+
+		$this->assertTrue($addressBookImpl->isSystemAddressBook());
+	}
+
+	public function testIsShared(): void {
+		$addressBookInfo = [
+			'{http://owncloud.org/ns}owner-principal' => 'user1',
+			'{DAV:}displayname' => 'Test address book',
+			'principaluri' => 'user2',
+			'id' => 666,
+			'uri' => 'default',
+		];
+
+		$addressBookImpl = new AddressBookImpl(
+			$this->addressBook,
+			$addressBookInfo,
+			$this->backend,
+			$this->urlGenerator
+		);
+
+		$this->assertFalse($addressBookImpl->isSystemAddressBook());
+		$this->assertTrue($addressBookImpl->isShared());
+	}
+
+	public function testIsNotShared(): void {
+		$addressBookInfo = [
+			'{http://owncloud.org/ns}owner-principal' => 'user1',
+			'{DAV:}displayname' => 'Test address book',
+			'principaluri' => 'user1',
+			'id' => 666,
+			'uri' => 'default',
+		];
+
+		$addressBookImpl = new AddressBookImpl(
+			$this->addressBook,
+			$addressBookInfo,
+			$this->backend,
+			$this->urlGenerator
+		);
+
+		$this->assertFalse($addressBookImpl->isSystemAddressBook());
+		$this->assertFalse($addressBookImpl->isShared());
+	}
 }
diff --git a/lib/public/IAddressBook.php b/lib/public/IAddressBook.php
index b2c9a103c2..ed66af4aa1 100644
--- a/lib/public/IAddressBook.php
+++ b/lib/public/IAddressBook.php
@@ -107,5 +107,20 @@ namespace OCP {
 		 * @since 5.0.0
 		 */
 		public function delete($id);
+
+		/**
+		 * Returns true if this address-book is not owned by the current user,
+		 * but shared with them.
+		 *
+		 * @return bool
+		 * @since 20.0.0
+		 */
+		public function isShared(): bool;
+
+		/**
+		 * @return bool
+		 * @since 20.0.0
+		 */
+		public function isSystemAddressBook(): bool;
 	}
 }