  The status and accuracy of the precision Monte Carlo generators used for
luminosity measurements at flavour factories is reviewed. It is shown that,
thanks to a considerable, long-term effort in tuned comparisons between the
predictions of independent programs, as well as in the validation of the
generators against the presently available calculations of the
next-to-next-to-leading order QED corrections to Bhabha scattering, the
theoretical accuracy reached by the most precise tools is of about one per
mille. This error estimate is valid for realistic experimental cuts, appears to
be quite robust and is already sufficient for very accurate luminosity
measurements. However, recent progress and possible advances to further improve
it are also discussed.
