posted by John .
Customer Officer: May I have your declaration from, please?
Customer Officer : Sure. Please open your suitcase.
(Is the expression 'suitcase' correct in this situation? Do you have some other suitable expressions? Correct the errors, plese.)
In your first sentence, the word needs to be "form" not "from" -- this is a typo I make all the time, and I have to be very conscious of it since a spell-checker will never pick it up!
The use of the word "suitcase" is correct. You could also use "briefcase" or "attache" or "valise" or "bag."
In the United States, the term, "Customs Officer," is more likely to be used.