The same change can be made to each word below to create new ones. Can you determine what it is?

CUP
RAP
DIVE
EVENT

HINT:
The change involves the same two letters, in the same order.

Answer:

The letters ID can be added to or inserted into each clue to give a new word:

CUPID
RAPID
DIVIDE
EVIDENT

Credit: LA Times Crossword
Sylvia Bursztyn and Barry Tunick
ID REQUIRED