unusual but nor impossible. for example, say the trust held non-dividend paying stocks and sold some of these. the gain would be part or corpus (principal of the trust). unless directed by the trust to distribute the gains (or at the discretion of the trustee if permitted, the trust would pay any income taxes and thus distributions would be tax-free to you. we know nothing about the trust's assets or its provisions. in you are concerned contact the trustee for an explanation.
