To reset identity column value and start value from “1” during insert new records we need to write query to reset identity column value. Check below Query
DBCC CHECKIDENT (Table_Name, RESEED, New_Reseed_Value)
Table_Name is name of your identity column table
RESEED specifies that the current identity value should be changed.
New_Reseed_Value is the new value to use as the current value of the identity column.
EX: DBCC CHECKIDENT ('UserDetails', RESEED, 0)
Once we run the above query it will reset the identity column in UserDetails table and starts identity column value from “1”