If you have doubts about the identity of the person making the request you can ask for more information. However, it is important that you only request information that is necessary to confirm who they are. The key to this is proportionality.
You need to let the individual know as soon as possible that you need more information from them to confirm their identity before responding to their request. The period for responding to the request begins when you receive the additional information.
If you process a large amount of information about an individual, you may ask them to specify the information or processing activities their request relates to before responding to the request. However, this does not affect the timescale for responding – you must still respond to their request within one month.
This FAQ is in these categories: DSAR questions