Is entitledto.com right about tax credits

Hi all, I've just been on the site entitledto.com to calculate what my tax credits would be should I start working part time. Partner works 20 hrs a week. According to the calculation, my child tax credit and his working tax credit wouldnt change should I earn around £150 a week. Does anyone know if this is right or have I miscalculated?

Why not give Inland Revenue a quick ring they will be 100% correct.

Willdo, will post what they say just incase anyone else wants to know, ta.

Ok... hmmmm right.. got through straight away, thats never happened before (nearly fainted)... She said that this year the award wouldnt change but as there would be more income in the next year it would be re-evaluated for the next award with the new earnings, and it may lessen. But... I'm not gifted in the brain department... but if I'd put hypothetical earnings in the calculation on entitledto.com plus my partners actual earnings for last year and it came up with the same amount of tax credits as we've got now, I'm confused. She said something about a £25,000 tax bracket, and when there start getting technical like that I kinda switch off lol... Suffice to say I think I'll go for it.