Qualified disasters to take a casualty loss in 2020 include disasters declared by the president under section 401 of the Stafford Act declared between January 1, 2018 and February 17, 2020. The loss needs to have occurred before January 19, 2020.
It also includes disasters declared by the president under section 401 of the Stafford Act before February 26, 2021 and that occurred between December 28, 2019 and December 27, 2020 and continued no later than January 26, 2021. However, this doesn't include major disasters that have been declared only due to COVID-19.
The California wildfires in January 2018 don't count for this specific relief.