When crossing the border, insurance is usually not needed. However, when entering some countries, mainly the Schengen Area, insurance is required, so when crossing the border it must be with you (not necessarily in paper form on official letterhead, it can be a printed electronic policy). In addition, you need to make it in advance, even when preparing a trip, since some states require insurance when considering issuing you a visa.
Insurance is necessary, first of all, for personal safety. It is not difficult to arrange it, just use the search form that will allow you to choose the most suitable option for your holiday and issue an insurance policy online*:
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