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With the approaching start-up of the experiments at LHC, the urgency toquantify systematic uncertainties of the generators, used in the interpretationof the data, is becoming pressing. The PHOTOS Monte Carlo program is often usedfor the simulationof experimental, selection-sensitive, QED radiativecorrections in decays of Z bosons and other heavy resonances and particles.Thanks to its complete phase-space coverage it is possible, with noapproximations for any decay channel, to implement the matrix-element. Thepresent paper will be devoted to those parts of the next-to-leading ordercorrections for Z decays which are normally missing in PHOTOS. The analyticalform of the exact and truncated (standard) kernel used in PHOTOS will beexplicitly given. The correction, being the ratio of the exact to theapproximate kernel, can be activated as an optional contribution to theinternal weight of PHOTOS.  To calculate the weight, the information on the effective Born-level Z/gamma*couplings and even directions of the incoming beams, is needed. A universalimplementation would have made the PHOTOS solution less modular and lessconvenient for the users. That is why, for the time being, we will keep thecorrecting weight as an extra option, available for special tests only.  We will quantify the numerical effect of the approximation with the help of amultitude of distributions. The numerical size of the effect is in generalbelow 0.1%; however, in some corners of the phase-space (well defined andcontributing less than 0.5% to the total rate), it may reach up to about 20% oftheir relative size.Comment: 23+1 pages 6 groups of figure

Next-to-leading logarithms and the PHOTOS Monte Carlo