1. May I have your student ID card number?

2. May I have your student ID number?
(Are both correct? Do you omit 'card' frequently?)

I think you should omit the the card. It makes more sense without it

Angelina is right. Sentence 2 is the better sentence.

Both "student ID card number" and "student ID number" are correct phrases, but they may be used in slightly different contexts.

1. "May I have your student ID card number?" implies that you are requesting the specific number assigned to a student ID card. In this case, the focus is on the physical card that the student carries.

2. "May I have your student ID number?" implies that you are requesting the unique identifier associated with a student. This number is typically a numerical code used to identify a student within a system or database. It is not specifically tied to a physical card.

In general, the term "student ID number" is often used more frequently and may be understood as a request for the unique identifier, regardless of whether a physical card is involved. However, if the context clearly indicates that the card itself is the focus, then "student ID card number" would be more appropriate.