1. An issuing Member State shall be responsible for ensuring that the data are accurate, up-to-date, and entered and stored in SIS lawfully.
2. Where an issuing Member State receives relevant additional or modified data as listed in Article 20(2), it shall complete or modify the alert without delay.
3. Only the issuing Member State shall be authorised to modify, add to, correct, update or delete data which it has entered into SIS.
4. Where a Member State other than the issuing Member State has relevant additional or modified data as listed in Article 20(2), it shall transmit them without delay, through the exchange of supplementary information, to the issuing Member State to enable the latter to complete or modify the alert. The data shall only be transmitted if the identity of the third-country national is ascertained.
5. Where a Member State other than the issuing Member State has evidence suggesting that an item of data is factually incorrect or has been unlawfully stored, it shall, through the exchange of supplementary information, inform the issuing Member State as soon as possible and not later than two working days after that evidence has come to its attention. The issuing Member State shall check the information and, if necessary, correct or delete the item in question without delay.
6. Where the Member States are unable to reach an agreement within two months of the time when evidence first came to light as referred to in paragraph 5 of this Article, the Member State which did not enter the alert shall submit the matter to the supervisory authorities concerned and to the European Data Protection Supervisor for a decision, by means of cooperation in accordance with Article 57.
7. The Member States shall exchange supplementary information in cases where a person complains that he or she is not the intended subject of an alert. Where the outcome of the check shows that the intended subject of an alert is not the complainant, the complainant shall be informed of the measures laid down in Article 47 and of the right to redress under Article 54(1).