The amount you are charged is not that high. Alas, spending even one day in Norwegian sector will attract tax. This assumes the work you were doing was Oil or Gas related, if it wasn’t and you were on a ship, you should not be paying their tax.
You have to pay Standard tax (28%), Top tax (another 9% or 12% depending on your earnings). You should also get registered to be exempt their National Insurance (that will save 7 odd %), this is normally done by the Employer, don’t know how its done for a Agency. You need a completed for E101 from the UK to show Norway you are paying National Insurance here.
Norway have a Seamans deduction scheme similar to the UK, you need to work at least 130 days onboard vessels that are registered to work in Norway (i.e. you don’t actually have to work that long in Norway as long as the vessels are registered to work there). You can claim back 30% tax up to a max NOK80,000.
You also get a small tax free allowance for each day. You would need to fill in a Norwegian Tax Return to be able to claim it and/or the Seamans deduction. You will never be able to get all of your tax back.
Further details at http://www.yourtaxoffice.co.uk/pageview.php?page=Norway-Tax-Guide, http://www.deloitte.com/assets/Dcom-Germany/Local%20Assets/Documents/04_Steuerberatung/2011/Norway.pdf (out of date but gives you an idea), http://www.nav.no/English
Would recommend speaking with an Accountant familiar with Uk Offshore Workers working in Norway.
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