fib Model Code 2010 (MC2010). MC2010 is based on the critical shear crack theory proposed by Muttoni, which relates shear resistance to the width of the so-called ‘critical shear crack’ which depends on slab rotation. Parametric studies are presented that show BS 8110 to require significantly less shear reinforcement within 1·5d (where d is the slab effective depth) of the loaded area than EC2 and MC2010, both of which have been extensively calibrated against test data. This raises the question of whether flat slabs designed to BS 8110 have an adequate factor of safety against punching failure. This question is explored using nonlinear finite-element modelling in conjunction with MC2010 Level IV. It is shown that punching resistance at internal columns can be increased significantly by restraint from the surrounding slab but the strength increase is variable and, in the case of uniformly loaded slabs, already largely included in BS 8110 and EC2.