What tends to raise concern
Trustees owe duties of loyalty and care to the beneficiaries, and a breach of trust can involve self-dealing or mixing trust money with the trustee's own funds. Sometimes the concern is simpler: the trustee will not say what the trust holds or why nothing has been paid. Not every disappointing result is a breach, since many trusts give the trustee broad discretion, and investments can lose value even when decisions were reasonable. The trust instrument itself matters a great deal, because it can expand, limit, or shape the trustee's powers.
Records a beneficiary can ask for
Start with a copy of the trust instrument and any amendments, and gather whatever statements, tax documents, and letters you have received. Beneficiaries are generally entitled to information about the trust, and a written request for an accounting is often the first formal step. Note when you first learned of the trust and of the events that concern you, because timing can affect deadlines. If you are worried that assets are being moved or sold, tell your lawyer quickly, since courts can act on an urgent basis in some situations. Keep communication with the trustee civil and in writing, and hold off on accusations until the documents have been reviewed.
Where a dispute goes
In New York, many trust disputes are heard in the Surrogate's Court, which can compel a trustee to account, rule on objections that beneficiaries file to that accounting, and in appropriate cases remove a trustee or order the trustee to restore losses. Some matters are brought in the Supreme Court instead, depending on the trust and the relief sought. A good number of disputes are resolved through negotiation once an accounting is on the table. Reading the trust document alongside what you have been told, and noting what is missing, lets us discuss whether an informal request, a demand letter, or a court petition fits the situation. Family relationships are part of that discussion, because the way a dispute is raised can affect them for years.