Depends what's inside. If you are bringing some items like I brought in some new instruments from Canada last week which I bought on line, they asked me the same luckily I had the bill (recite) in my email so I just printed that out and presented it.

Actually the customs authority is suppose to put 2% charge for bringing the item from out side, so they just wanna see the bill for how much you have paid.

If you get the bill with you no hassles they will claim 2% are you are done.

Hope it helps