Read the contract before doing anything else
Most agreements say more about what happens next than people remember. Look for a notice provision and a chance to cure, because skipping a required notice can undercut a claim no matter how clear the breach was. Look for where disputes are supposed to go, since an arbitration clause or a venue provision may take the decision out of your hands. Look for fee shifting, limits on the types of damages recoverable, and any cap on the total. A clause nobody discussed at signing often controls more of the outcome than the breach itself. Then decide whether to keep performing or stop, because that choice can change your position either way.
What you would need to show
The agreement as it actually stood, including amendments, purchase orders, and the email exchanges that quietly changed terms along the way. What each side did and when, supported by invoices, delivery records, and payment history rather than recollection. What the failure cost you, calculated in a way someone else can follow. And what you did to limit the loss afterward, since that question comes up in nearly every contract matter. Where performance was accepted for a while without objection, the correspondence from that period usually matters more than anything said later.
Weighing whether to proceed
Who the other side is comes first. A company still operating with assets or insurance is a different proposition from one that has wound down, and a claim you cannot collect on is an expensive way to be right. Then the amount, since smaller matters may fit a simplified court part where the process is shorter and less costly. Then time and attention, which is the cost owners underestimate most. Time limits also apply, and how long you have varies by state and by what kind of claim it is. Often the better result is a negotiated resolution that preserves the receivable, and we will say so when that is what the situation calls for.
