High phosphorus (P) content in feeds of laying hens can decrease their performance. In the Czech Republic phytase has been routinely added at 375-500 FTU per kg of feeds containing 0.38% available P. This combination is wrong as it increases percentage of eggs with damaged shell. P requirement depends on the composition of feeds. Thus, we recommend available P concentration of 2.7g per kg of wheat-containing feed mixture and 3.0 g per kg of maize-containing feed mixture. We also recommend to reduce the phytase supplement to 150 FTU/kg. In this way the cost of feeds and P excretion in faeces can be decreased without a reduction of performance.