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More than 272 Romanian companies are registered in Bulgaria and file their tax declarations there.
In 2006, one year before Romania and Bulgaria's EU accession, only 33 Romanian firms were registered in Bulgaria.
Bulgaria's low corporate tax rate of 10% has apparently encouraged this trend as Romania's own rate reaches 16%.
But the number of Greek companies registered in Bulgaria appears to be much higher. Over the last year, 2,072 Greek firms have filed their tax declaration in Bulgaria. The corporate tax rate in Greece is 25% (see 'Background').
More than a third of the Romanian companies registered in Bulgaria (93 to be precise) are headquartered in Ruse, a city just across the Danube River, 70km from the Romanian capital Bucharest. Another 93 are registered in Sofia and 22 in Varna, on the Black Sea coast.
According to the Romanian tax office, the fact that many firms decide to establish their headquarters in Bulgaria is due to the low tax rates, but also less burdensome procedures for setting up a business.
Experts say another factor could be the macroeconomic stability in Bulgaria and the fact that the national currency is pegged to the euro at a fixed rate.
Bulgaria's lower wages and rents are also valuable attractions for investors. However, Bulgarian Finance Minister Simeon Djankov believes this will not last for long, saying he expected income levels in Bulgaria to exceed Romania's over the next two years.
Speaking on bTV channel, Djankov said GNP per capita in Bulgaria currently stood at 43% of the EU average, while in Romania it was a bit higher, at 45%.
According to the World Bank, GDP per capita in Bulgaria is 6,423 dollars per year, compared to 7,500 for Romania and 29,240 for Greece. In comparison, the same statistics put the figure at 105,044 for Luxembourg, 55,992 for Denmark, 47,917 for the Netherlands, 45,562 for Austria, 44,581 for Finland, 43.671 for Belgium. France ranks lower with 41,051, followed by Germany at 40,670. The UK is further down at 35.165 dollars per year. Portugal, another debt-stricken country like Greece, is at 21.903, well below the EU average of 32.845 dollars per year (22.930 euro).