You are required to have an insurance policy that covers trekking to 5,545m, but it does not need to cover technical climbing. You're advised to take out insurance to cover potential events that might cause you to cancel your trip. You should bring with you a copy of your policy and also a photocopy of your passport, and to keep it separate to your own documents in the unlikely event that you lose your passport. We advise you to consider the British Mountaineering Council insurance, but many other insurance companies offer policies suitable for Everest Base Camp, such as truetraveller, DOGTAG & others.