In response to the Rudd government's bombshell last Sunday, the 40 per cent resource super profits tax, Moody's said the 'A1/P-1' long- and short-term credit ratings assigned to BHP Billiton will not be immediately affected by the new tax. Similarly, the 'Baa1/P-2' ratings assigned to Rio Tinto will be unaffected. Given that RSPT will be phased in from the fiscal year ending 30 June 2013, Moody's said it would be too early to measure its precise impact at this point. However, if RSPT was applied to FY 2009 results, BHP Billiton's operating profit would have been lower by around 15 per cent to 20 per cent. The earnings impact would be less under a higher price environment. Fitch also advised that its ratings on BHP Billiton, 'A+/Stable' and Rio Tinto 'A-/Stable', will be unaffected.