Sentence 1The controller shall communicate any rectification or erasure of personal data or restriction of processing carried out in accordance with Article 16, Article 17(1) and Article 18 to each recipient to whom the personal data have been disclosed, unless this proves impossible or involves disproportionate effort.notify each recipient
Sentence 2The controller shall inform the data subject about those recipients if the data subject requests it.name them on request
In short

Article 19 makes sure a correction, deletion or restriction doesn’t stop at your own systems. When you act on a request under Articles 16, 17(1) or 18, you have to tell everyone you disclosed the data to, unless that’s impossible or would take disproportionate effort. And if the person asks, you have to tell them who those recipients are.

In Proximus, the Court of Justice read Article 19 together with the accountability rules to require a directory provider to pass a consent withdrawal on to the other directory providers it supplied and, in the circumstances of that case, to the operator that supplied the data. Sweden reprimanded Klarna for not telling a customer which recipients had received his data. And authorities in Spain and Sweden fined Google over the reverse problem: passing details of removal requests to parties the law didn’t require it to tell (AEPD, €10.000.000; IMY, final fine SEK 50.000.000).