I requested for a subject access request from the UK border control but I need to know how much time do they need to verify my identity . How much time does the whole entire process take ?
Your SAR application will not be accepted until UKVI receive your evidence of identity documents, and it will be automatically rejected if you do not send them within 15 days of making your application. Once your identity has been verified, you should receive a response within 30 days.
The overall timeline from receipt of evidence documents to receiving a response should not exceed 40 days https://ico.org.uk/media/for-organisations/documents/2259722/subject-access-code-of-practice.pdf#page8
According to the Information Commissioners Office, Subject Access Requests are subject to a 40 calendar day response time limit.
What is the time limit for responding?
In most cases you must respond to a subject access request promptly and in any event within 40 calendar days of receiving it