Theoretical error of luminosity cross section at LEP

The aim of this note is to characterize briefly main components of theoretical error of the small angle Bhabha measurement at LEP and to discuss critically how solid these estimates really are, from todays perspective. We conclude that the existing theoretical error of the LEP luminometer process (small angle Bhabha) is rather solid, and we add some new discussion concerning the remaining uncertainties and prospects of the future improvements toward the ≤ 0.025% precision. Invited talk presented at Mini-Workshop “Electroweak Physics Data and the Higgs Mass”, DESY Zeuthen, Germany, February 28 March 1, 2003. ⋆ Work partly supported by the European Community’s Human Potential Programme under contract HPRN-CT-2000-00149 “Physics at Colliders”, by Polish Government grants KBN 5P03B09320 and 2P03B00122,