Using a 20-year-long, population-wide panel with detailed firm and group level data from Norway, we study the profitability change in companies that shift from being domestic to being multinational as well as companies that shift from being multinational to being domestic. Profitability falls when domestic companies become multinational and increases when multinational companies become domestic. The average change in profitability is about 24%, all else equal. We attribute our findings to the profit shifting opportunities that are available for multinational companies, and we display several patterns in the data that are consistent with this interpretation. We find that the extent of profit shifting decreases after the introduction of stricter transfer pricing regulations, and an increase in transfer pricing audits, starting in 2007/2008. Our best estimate of the total corporate tax revenue lost due to profit shifting is about 6% in the last year of the sample, 2012. We estimate that the revenue loss would have been twice as large in absence of the new regulatory framework.