NNLO initial-state corrections to $e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-}\gamma$

We present initial-state corrections to $e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-}\gamma$ at next-to-next-to-leading-order in QED for several experimentally motivated scenarios up to a few GeV. We include photonic as well as vacuum-polarisation corrections into the Monte Carlo framework McMule that allows for the calculation of arbitrary infrared-safe observables. For the total cross sections, the corrections are typically below the percent level, but they can be locally larger in distributions. The vacuum-polarisation corrections are of similar size and must not be neglected, in particular for larger centre-of-mass energies.