Leteer of Undertaking (LUT)

LUT will be valid for a financial year. If LUT was furnished in FY 2019-20, then the date of expiry of the validity of such LUT is 31st March 2020. Therefore, You need to furnish fresh LUT for FY 2020-21. The time limit to furnish such LUT for FY 2020-21 is extended from 31st March 2020 till 30th June 2020.

Sir, this is not my query.
I explain my query through an example.
Suppose, somebody has given me their GST number we can check wheather its valid or not by searching it on GST portal. Likewise, I want to know, if a third party has given me their LUT certificate, how can I check if it's correct or not ?