How long do you have to collect a unpaid debt? If a client refuses to pay an invoice for work completed, how long do you have to file a claim? I have a written contract but they sent me a letter canceling the agreement.
The statute of limitations in Oregon appears to be six years (per the link provided by Nate Eldgredge in the comments). This would be extended if there was a partial payment or written affirmation of the debt by the debtor.
In general you can dispute and negotiate any bill from a professional. The stronger your arguments for disputing it, and the more coherent your demands for adjustment, the more successful you will tend to be. This is like any business negotiation. One partner at a very large U.S. law firm once admitted to me that their corporate clients almost always ask for &ndash; and receive &ndash; billing adjustments. Of course, when push comes to shove, unless you're accusing the lawyer of fraudulent billing, then typically by contract you are liable for the bills. However, non-lawyers often assume that they will lose any dispute with their lawyers because it seems like lawyers have free access to the legal system. The reality is that there is a significant threshold that must be met before a law firm will sue a client for payment. That threshold will depend on the firm's opportunity costs, the costs of litigation, their assessment of reputational risks, how much they expect to actually collect, and sometimes just how ticked off they are.
If you are going to sue, and can prove they overcharged - consider going to the small claims court. It should cost you $15 + time - unless you loose quite badly - in which case its conceivable the court could award costs against you (I don't know if this is true of the small claims court in NY). You can represent yourself, so no heavy legal bills. It will take a a few hours of your time to prepare and have the hearing. Of-course, very often, just by filing you will get the opposing party to sort out the issue - and probably won't even need to go to court.
It is not necessary for an agreement to be verbose and written by a lawyer, for it to be binding. There is some danger in having untrained people writing up agreements (they don't know the distinction between "what the law says" versus "what we had in mind"). The agreement is binding, but their interpretation of the contract language does not automatically prevail. The statement "ALL TUTORS ARE PAID 8 HOURS, unless told otherwise" is slightly problematic since it is not true (you can't pay time, you pay money for time spend). With no other statements about time and payment, and just looking at the words, this says that an employee will be paid for 8 hours work, period. Unless they say something different. That could mean "even if you work 20 hours, you only get paid for 8" (illegal under various labor laws), or it could be "even if you only work 2 hours, you get paid for 8" (the most reasonable interpretation). The interpretation "You are limited to 8 hours of work per pay period / contract" is not a reasonable interpretation: that isn't what the clause says. Such a limit could be clearly expressed ("can work up to 8 hours" is a clear way to state the limit), and since they didn't say anything like that, that is not how the courts will read the clause. They can, however, inform you otherwise, e.g. say "your minimum automatic pay is now 2 hours", or "we will only guarantee 2 hours work", and at that point that's what the number is. Since this is (presumably) a take-it or leave it contract which they wrote up and you didn't actually negotiate, any unclarities are legally interpreted in your favor. If you have worked more than 8 hours and they are using the contract language to argue that you won't be paid for the overage, that is not at all likely to hold up in court. Under terms of the contract (interpreted as stating a minimum guarantee of hours), they can inform you that your new minimum is 0 hours. Also, unless there is some kind of tenure clause, they can terminate the contract at will, and maybe they'll hire you under a different contract. What the terms of employment were for you in the past does not matter, what matters is what the current terms are. If you did not pay attention to the fact that they changed the terms of the agreement as of this quarter, that is not their problem. If they decided to change to "actual hours worked" after the current contract was formed, and they informed you of that fact later, then thereafter that is what the agreement is. Until you are notified of that change, the guaranteed minimum is what it says in the contract. In case their argument is "The university sets this policy, the department made a mistake in not informing you", the university has to take responsibility for the errors of their inferiors.
To start with, this is a highly technical issue upon which different jurisdictions may differ, and in which different rules may apply in different circumstances either by agreement or by statute. Also, similar situations are sometimes treated differently in this regard in bankruptcy and out of bankruptcy. The majority rule is that the lender may choose which remedies - such as collateral and guarantee rights, to enforce, and the lender may choose in which order to enforce them. For example, most jurisdictions allow a lender to collect from a guarantor even when collateral is available to the lender, in lieu of foreclosing on the collateral. Sometimes, however, special rules apply. For example, if the guarantor is a government agency (e.g. the Small Business Administration or the Veteran's Administration), often the lender is required to take all reasonable efforts to collect from the borrower and recover the amount owed from collateral, before the guarantee can be invoked. Similarly, sometimes the law distinguishes between an accommodation party who receives no consideration in a transaction who signs as a direct debtor, and one who signs in a guarantor capacity. Those jurisdictions may require a good faith effort to collect from direct debtors (often including attempts to foreclose upon collateral) before attempting to collect from guarantors who sign as such. There are also arrangements, such as credit default swaps or a situation when a consumer provides a credit card payment authorization which a creditor can use in the event of a default (or the large dollar amount equivalent of such an arrangement called a "letter of credit"), in which the line between what constitutes collateral and what constitutes a guarantee can be blurred.
The issue of who pays directly for the items and/or to contractors is irrelevant. The important thing is to memorialize the agreement/arrangement in writing so as to preempt or solve eventual disputes. A clearly written agreement signed by the parties would supersede any presumption of conditions and rights arising solely from the parties' conduct.
Small claims court was created for such matters. There is the possibility of a fee waiver, and if you prevail, you could get some of your costs covered (though there are other hoops to jump through if you need enforcement). A formal letter (written by you) stating that you intend to seek a legal judgment against him/her in the amount owed might be sufficient motivation for the person to pay what is owed.
A contract need not be written to be valid and enforceable. However, if there is no written contract, then in a dispute the burden of proving (via a preponderance of evidence) a contractual obligation falls on the party asserting it. In the scenario you describe it sounds like that would be impossible for the processing company.