@mpjgregoire It's not how taxes work, exactly. There's a per-child benefit in the UK for lower- and middle-income families, of which you got 100% if your income was less than £50k, 0% above £60k, and in between it was linearly prorated. The IFS credited in the image footer appears to be an anti-tax org; I think they're the ones that characterize the reduction in benefit as "effectively a tax" and published the modified dataset with that "baked into" the tax rates. In April 2024 the thresholds were changed to £60k min, £80k max, so the graphic dates from before the change; today it would be twice as wide, half as high, and shifted rightward.