UK/Norway have a reciprocal agreement so UK residents will pay Norwegian tax if working in Norway.
The company usually pays the Norwegian side of that though!!!
Make that sometimes. many people "think" the Company pays any difference between what you would earn in the Uk and what you would earn in Norway. Unless you have what they call a net Wage Agreement, then they don’t.
For UK taxpayers, if you are working on an oil or gas related contract, you will pay Norwegian tax instead of Uk tax. Norwegian tax is not calculated the same as UK (you earn X amount at 0%, Y amount at 22% etc.)
You can earn so much a month without paying any tax (something like NOK3500 each month, but its pro rata so if you only work 2 weeks there you only get 0.5 the allowence etc.)
You get a 10% standard deduction for being a foreigner. Your company should do the paperwork to opt you out of paying Norwegian National Insurance equivalent.
Norwegian tax seems to work out at between 30 and 50%, when I last worked in Norway in the 90’s (doing all year month on/month off) I ended up paying 28% tax to Norway (but this was 10 years ago). It seems the more you work there the lower the percentage you pay work out. Thats why 1 off trips tend to make it liik like 40-50% tax.
If you work onboard vessels that are registered to work in Norway (note you do not have to do the work in Norway but the boat must be registered to work there) and you do more that 130 days on these vessels (but NOT vessels that are drilling, extracting or exploration, survey and construction should be fine), then you fill out a Norwegian Sefarers form and you will get a rebate of Norwegian tax on 30% of what you pay (up to a limit of NOK80,000).
If you are a UK higher tax payer and are not claiming your UK tax back, it can work out cheaper to do some of your work in Norway (as this reduces your liability to pay 40% in UK).
If you are claiming the Forerign Eranings Deduction for Seafarers from the UK, then obviously you lose out when you pay money to Norway as its only UK tax that you can claim back.
Some links for you:-
Norwegian Sefarers deduction 2008 http://www.skatteetaten.no/Templates/Artikkel.aspx?id=74831&epslanguage=NO
Various tax topics from the Norwegian Tax office http://www.skatteetaten.no/Templates/GenereltInnhold.aspx?id=9125&epslanguage=NO
Foreign Employers and Employees in Norway http://www.skatteetaten.no/Templates/Gruppe.aspx?id=9553&epslanguage=NO
General, taxes in Norway http://www.norway.org.uk/policy/tax/tax.htm