NES is non-effective-strength. If you don‘t show up for 5 consecutive parade nights without a leave pass, then you‘re declared NES. You‘ll receive a letter stating your status, and saying that you‘re no longer receiving pay/benefits from the military nor earning time in towards your CD or pension.
Once you return from your NES, you need to get permission from the unit to begin parading again. They can agree and reinstate you, or they can have you discharged. If, after receiving the letter, you still don‘t show up, you‘ll receive a bill from DND for all your kit which you must pay (or just return your kit), and you‘ll be dishonourably discharged from the military, thus preventing you from ever holding a government position. If you don‘t return your kit or pay for it, then it‘ll be assessed on your income taxes and then the feds come after you.
Moral to this story: parade regularly and don‘t disappear for long periods without explanation.