We present the analysis and results of a 20 ks XMM-Newton observation of RBS1423. X-ray spectral analysis is used to establish a significantly broadened relativistic iron K-alpha line from a highly ionised disk. A QSO at z=2.262 was considered to be the optical counterpart of this ROSAT Bright Survey X-ray source. Based on the improved XMM-Newton source position we identified a z=0.208 QSO as optical counterpart to RBS1423. The 0.2-12 keV X-ray luminosity of this radio-quiet QSO is 6x10^{44} erg/s. The XMM-EPIC spectra are well described by a power law with a significantly broadened iron K-alpha line. Disk line models for both Schwarzschild and Kerr black holes require hydrogen-like iron ions to fit the measured line profile. Significant ionisation of the reflection disk is confirmed by model fits with ionised disk models, resulting in an ionisation parameter xi~2000.
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