What kinds of legal claims typically come up in a business partner dispute like this?

Several distinct legal claims commonly arise together in a partnership dispute of this kind. Breach of fiduciary duty refers to a partner failing their legal obligation to act honestly and in the partnership's genuine best interest rather than their own personal interest. Breach of the partnership agreement or operating agreement itself covers violations of whatever specific written terms the partners agreed to. Conversion refers to one partner wrongfully taking or using partnership funds or property as though it were their own. And a demand for an accounting, a formal, legally compelled review and disclosure of the partnership's complete financial books and records, is frequently included as well.

The accounting claim in particular tends to function as the practical workhorse of these cases, since it legally compels the full disclosure of financial records you very likely need in order to actually calculate the specific dollar amounts underlying your other claims, especially where your partner has been controlling the books and you've had limited visibility into the partnership's actual finances.