New to a small sport club committee. Ex-chairman/treasurer has demanded reimbursement of expenses over the course of many years = $70K +. No paper trail. No contracts. No receipts. No annual financial statements.
First up, appoint one only Committee member to have carriage of this issue.
Pass a resolution that the only Committee member who will talk to him is <whoever>.
If willing and able, then Vice Presidents can be good for this kind of thing,
because they don't have any other specific responsibilities, and can still refer back to the President and/or Committee if they need to.
That way, when he contacts the other Committee members, they can decline to talk to him, with comfort and a clear conscience.
Second, the Committee should pass a resolution to the effect of:
"The Committee will not consider* expense claims from any member that are not reasonably able to be supported with records."
Has intimated legal action if not addressed by new committee.
Legal action about what?
Actions, omissions, poor decisions, and compliance failures, on
his watch?
Refusal to pay unsupported claims of money?
Perhaps he's threatening to defame individuals. He does so at his own legal risk.
Have a lawyer and an accountant go through the books and records.
Then, if all the ducks are in fact in order, then you're reply to any threats of legal action
might reasonably be
"Well, go on then."
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* "Consider" does not mean "pay"