What is undervalue and why it is done?
Undervaluing is declaring a lower price on a package than the actual value of the package. Mostly it's done to avoid import fees and other taxes. Since I live in the Netherlands, this blog will be about the Dutch situation. However, it can give a general idea why this shouldn't be done anyway. And for those who wonder; I never undervalued a package since I don't want to take the risks that come with doing it; here is why.
Examination by customs
If customs don't trust your declared value they have the right to take their very long time to examine your package, open it. If they suspect you declared a lower value they will send you a mail about it, asking for the real value of the package, or destroy the package if they suspect it are counterfeit goods. Since you are committing tax fraud with declaring a lower value you can also receive a fee, which generally in the Netherlands isn't cheap. Also the customs can press charges against you.
Loss of package
If your package gets lost in the mail and you declare a value of 10 euros for an item worth 300 euros you only will get paid 10 euros by insurance. So if your package does get lost there is no way in getting all of your money back if you use the undervalue method.
Long story short, don't cheat on customs and pay your taxes.