When can &quot;exact change&quot; policies be enforced?
<p>In general, <a href="https://law.stackexchange.com/a/11439/10">"exact change" policies are legal</a>.</p>

<p><a href="https://www.treasury.gov/resource-center/faqs/Currency/Pages/legal-tender.aspx" rel="nofollow noreferrer">The Department of Treasury provides this helpful explanation</a>:</p>

<blockquote>
  <p>The Coinage Act of 1965, specifically Section 31 U.S.C. 5103, entitled
  "Legal tender," ... states: "United States coins and currency
  (including Federal reserve notes and circulating notes of Federal
  reserve banks and national banks) are legal tender for all debts,
  public charges, taxes, and dues."</p>
  
  <p>This statute means that all United States money as identified above
  are a valid and legal offer of payment for debts when tendered to a
  creditor. There is, however, no Federal statute mandating that a
  private business, a person or an organization must accept currency or
  coins as for payment for goods and/or services. Private businesses are
  free to develop their own policies on whether or not to accept cash
  unless there is a State law which says otherwise. For example, a bus
  line may prohibit payment of fares in pennies or dollar bills. In
  addition, movie theaters, convenience stores and gas stations may
  refuse to accept large denomination currency (usually notes above $20)
  as a matter of policy.</p>
</blockquote>

<p>But in practice doesn't this mean that "exact change" policies can only be enforced when payment is required <em>before</em> a good or service is provided?  Because I can incur a debt in most commercial situations.  E.g.:</p>

<ol>
<li><p>I drive into a parking garage that lists rates on a sign that also warns, "Exact change required."  Later when I go to leave I am asked for exact change at the exit.  I say, "Well, I don't have exact change, but I do owe you money for parking here.  Federal law says I can satisfy this <em>debt</em> with legal tender.  So start counting the pennies, or just let me out!"</p></li>
<li><p>I go into a store that says, "No bills larger than $20 accepted."  While shopping I drink a soda and eat a few snacks.  I go to check out and all I have is a $100 bill.  Once again I say, "All I have is this $100 bill.  I am in <em>debt</em> to you for the food I've already consumed, and this bill is legal tender for satisfaction of that debt.  Either make change or thank you for the free snack."</p></li>
</ol>

<p>I get in a taxi, enjoy a meal in a restaurant, etc.  All of these are paid after the service has been consumed.  Are they not then debts that must be discharged if I offer legal tender?</p>

<p>If a business literally has an &quot;exact change only&quot; policy, that can't be enforced in post-pay situations. But if they have a &quot;you are free to overpay, but we won't give you change back&quot;, that's different, especially if it's communicated from the beginning. If they tell you they don't give change, then you're taking their goods/services implicitly agreeing to their terms.</p>

<p>I provided an answer to a similar question regarding paying with pennies <a href="https://law.stackexchange.com/a/9113/2690">here</a>. I touch on what I think is a conceptually related issue related to restrictions on methods of payment after service is rendered in an answer <a href="https://law.stackexchange.com/a/13910/2690">here</a>.</p>

<p>Perhaps a fully generalized answer might be as follows: unless the payee can demonstrate that the payer knew, or that the payer reasonably should have known (that is, it would have been unreasonable for the payer to have believed differently), about the restrictions, the payer must inevitably be allowed to satisfy the obligation without regard to the restrictions on the method of payment.</p>

<p>It would be unreasonable to expect to be able to pay in seashells, but not in pennies; it would be unreasonable to expect to be able to pay a $5 bill by signing over a car title and expecting change, but not by paying with a $10 bill and expecting change; etc. Unless the restriction is material to the agreement, reasonable and explicit, ultimately it would seem like it has to be unenforceable. Not that the payer has to pay, of course, but that the payee can demand payment in a specific form.</p>

<p>Consider cases where this is not true. Specific performance may be requested in some cases, and perhaps if method of payment is material and reasonable in some context one could sue for specific performance by the payer. I am not a lawyer and I don't know if it is even possible to legally distinguish between the act of delivering specific kinds of tender and the act of paying an equivalent amount in any tender, especially where paper money and coins are concerned. But these are interesting questions.</p>

united-states legal-tender