Considerable variations exist in UK practice for the design of flexural reinforcement normal to the slab edge at perimeter columns of flat slabs. Differences in practice include designing the reinforcement at the slab edge for the moment at the column face, the moment at the column centreline and neglecting moment transfer altogether. This paper uses the critical shear crack theory (CSCT), as implemented in fib Model Code 2010 Level of Approximation IV and a Joint Shell Punching Model developed by the authors, to investigate the influence of variations in flexural reinforcement detailing on punching resistance at edge and corner columns of full-scale flat slabs with shear reinforcement. Comparisons are made with strength predictions obtained with BS8110, EN 1992–1-1:2004 (EC2–04), fib Model Code 2010 and EN1992–1-1:2023 (EC2–23) which incorporates the CSCT. BS8110 and EC2–04 relate punching resistance to the flexural reinforcement ratio. Hence, designers commonly increase punching resistance at edge and corner columns by providing surplus flexural reinforcement normal to the slab edge. The paper shows that the influence on punching resistance of the reinforcement ratio normal to the slab edge is less than implied by BS8110 and EC2–04. Recommendations are made for the design and assessment of punching resistance at edge and corner columns of flat slabs.