Rate and $CP$-asymmetry sum rules in $B\to K\pi$

The observed violation of $A_{CP}(B^0\to K^{+}{\pi }^{-})=A_{CP}(B^{+}\to K^{+}{\pi }^0)$ has been recently mentioned as a puzzle for the standard model. We point out that while this violation may be accounted for by a large color-suppressed tree amplitude, a sum rule involving three or four $B\to K\pi$ $CP$ asymmetries should hold. The current experimental status of these sum rules and of a sum rule for $B\to K\pi$ decay rates is presented.