State-run power major NTPC today said that due to lower interest income and income tax refunds in 2009-10, the company reported a marginal growth of 5.5 per cent in the provisional profit after tax. Briefing reporters in New Delhi today, Chairman and Managing Director NTPC R S Sharma said the company has recorded the profit after tax of 8,656 crore rupees in 2009-10 due to lower interest income and income tax refunds.