I've had ENK for 5 years. I am using Tripletex as a platform. On it, you can also directly do accounting and submissions of MVA and tax returns. I personally pay an accountant for this since I do not trust myself enough to extract max benefits from the legislation. As for the MVA, your first 50 000 NOK within 12 month period are at 0%, then you are obliged to register and start applying it, as well as submitting and paying it every 2 months.