K. K. Madsen, C. E. Grant, V. Burwitz, H. Earnshaw, K. Forster, M. Guainazzi, V. L. Kashyap, H. L. Marshall, C. B. Markwardt, F. Meeker-Fürst, E. D. Miller, L. Natalucci, P. P. Plucinsky, M. Shidatsu, H. Suzuki, Y. Terada, A. Tümer

In this report we summarize the activities of the International Astronomical Consortium for High Energy Calibration (IACHEC) from the 18th IACHEC Workshop at Pelham, Germany. Fifty-six scientists directly involved in the calibration of operational and future high-energy missions gathered during four days to discuss the status of the cross-calibration between the current international complement of X-ray observatories, and the possibilities to improve it. This summary consists of reports from the Working Groups with topics ranging across: the identification and characterization of standard calibration sources, multi-observatory cross-calibration campaigns, appropriate and new statistical techniques, calibration of instruments and characterization of background, preservation of knowledge, and results for the benefit of the astronomical community.