A volunteer or community group is a type of non-profit organization, designed to enrich the local community or volunteer for specific causes. An informally organized non profit or community group is not legally required to have an EIN, but there are situations in which an EIN might become necessary. For instance, if the community group wants to open a group bank account, they will need to create a formalized structure, and apply for an EIN.
Community/volunteer groups will also need an EIN for other tasks, such as applying for permits and licenses. When hosting public, city events, these may be necessary. But until the organization has to organize an as an official non profit organization, it may be able to operate informally. Once the community/volunteer group has been properly structured, it will need to file its taxes every year—even though it has non profit status. Non profit organizations still need to obtain EINs to file taxes, they simply have an exemption from paying them.