Actually your tax credits for 2005 are €1,580 single person's credit and €1,270 PAYE credit. See [broken link removed]. A significant quirk of Karl's calculator is that he still uses a tax free allowance approach to calculating figures in order to maintain easy backward compatibility with pre-tax credit tax years. This is how he simplifies matters in order to support calculating figures for many years back. However it does make things confusing on closer examination. Basically the tax credits above have been converted into standard rated tax free allowances as follows: €1,580 / 20 * 100 = €7,900 and €1,270 / 20 * 100 = €6,350. Not sure how much sense that makes but the final figures are the same and should be correct unless you have other credits or allowances not catered for by the calculator. Hope this helps.