A sum certain is a specific dollar amount that is either stated outright in a document or can be worked out from the document’s own terms with simple arithmetic. The idea matters because when a debt qualifies as a sum certain, you can collect it through faster, cheaper legal procedures, including a default judgment entered by a court clerk without a judge ever weighing in. It also decides whether a written promise to pay counts as a negotiable instrument under commercial law.
What Makes an Amount a Sum Certain
The test is self-containment. If you can read the contract, note, or invoice and know exactly what is owed without pulling in outside evidence or asking someone to render an opinion, you have a sum certain. Three features show up again and again:
- Fixed by agreement. The parties wrote down a specific figure, like a $10,000 loan or a $500 service fee.
- Determinable by formula. The document supplies enough to calculate the number, such as principal plus interest at a stated rate over a stated period.
- Self-contained. No appraisals, no market data, no expert testimony, no jury assessment is needed to arrive at the figure.
That last trait is the one that does most of the work. The moment a calculation requires someone’s judgment, the amount stops being certain. A legitimate claim can still exist; it just has to travel a different procedural road.
What Counts and What Doesn’t
A promissory note for $10,000 payable on a specific date is the textbook example. So are an unpaid invoice for $500 in repair work, a $2,400 rent payment due on the first of the month, and a bounced check for $750. In each case, the document names the number.
Liquidated damages clauses can produce a sum certain too. If a construction contract says the contractor owes $100 per day for every day of late completion, and the job runs 30 days long, the amount is $3,000. No expert needs to testify.
Several common claims fall on the other side of the line. Pain and suffering in a personal injury case. Lost profits from a business disruption. Damage to reputation. The reasonable value of services where no price was agreed. Each of these demands evidence, argument, and ultimately a decision-maker to settle on a figure. They are not sums certain, however valid they may be.
Why It Matters in Default Judgments
The sum-certain concept carries the most practical weight when a defendant fails to answer a lawsuit. What happens next depends almost entirely on whether the plaintiff is asking for a fixed amount.
Clerk-Entered Judgment
Federal Rule of Civil Procedure 55(b)(1) lets the court clerk enter a default judgment when the claim is for a sum certain or an amount that can be made certain by computation. The plaintiff files a request with an affidavit showing the amount due, and the clerk enters judgment for that amount plus costs.1Legal Information Institute. Federal Rules of Civil Procedure Rule 55 – Default; Default Judgment The route is closed if the defendant is a minor or someone the court treats as incompetent.
The affidavit has to show the math. Original amount owed, payments received, how the current balance was calculated. For a straightforward invoice, that might be a one-page document. For a loan, it includes the principal, the rate, the accrual period, and the total. The clerk is verifying arithmetic, not making judgment calls.
Court-Entered Judgment
When the claim is not for a sum certain, the plaintiff must apply to the court under Rule 55(b)(2). The court can hold hearings, order an accounting, require evidence to establish the truth of the allegations, or investigate any other matter it needs to resolve before entering judgment.1Legal Information Institute. Federal Rules of Civil Procedure Rule 55 – Default; Default Judgment
The gap in time and cost is real. A clerk-entered judgment can be done in days. A court-entered judgment on unliquidated damages can require a hearing where the plaintiff presents evidence and the judge decides the amount. The defendant’s absence does not relieve the plaintiff of proving what the claim is worth. State procedural rules generally work the same way.
Interest, Attorney’s Fees, and Where the Line Blurs
The edges of “certain” get thin around interest and fees.
Interest at a fixed contractual rate on a known principal is typically treated as an amount that can be made certain by computation, which keeps the claim within the clerk-entry rule. A promissory note for $10,000 at 6% annual interest, with 18 months of nonpayment, produces a number anyone can calculate.
Attorney’s fees are harder. Many contracts promise “reasonable attorney’s fees” to the prevailing party, and reasonableness is inherently a judicial call. Federal Rule of Civil Procedure 54(d)(2) requires that a claim for attorney’s fees be made by motion, with the court setting the amount.2Legal Information Institute. Federal Rules of Civil Procedure Rule 54 – Judgment; Costs Even when the underlying debt is a clean sum certain, adding fees can push you off the clerk-entry path. The usual workaround is to get the clerk-entered judgment on principal and interest, then file a separate fee motion.
One more boundary. A default judgment cannot exceed what the plaintiff demanded in the complaint, whether or not the claim is for a sum certain.2Legal Information Institute. Federal Rules of Civil Procedure Rule 54 – Judgment; Costs A $15,000 demand caps the judgment at $15,000, even if later math would support more. Getting the numbers right in the initial filing is not optional.
Sum Certain in Negotiable Instruments
The term also appears in commercial law, where it decides whether a written promise to pay can circulate like a simplified form of currency. Checks, promissory notes, and drafts are candidates for this treatment, but only if they meet the rules.
Under Article 3 of the Uniform Commercial Code, a negotiable instrument must be an unconditional promise or order to pay a fixed amount of money, payable to bearer or to a specific person, and payable on demand or at a definite time.3Legal Information Institute. UCC 3-104 Negotiable Instrument The current language says “fixed amount of money” rather than “sum certain,” but the concept has not changed. If the face of the instrument does not tell you the amount owed, the instrument is not negotiable.
Variable interest rates do not break negotiability. The UCC allows interest to be stated at a fixed or variable rate, and even permits the instrument to reference outside information for setting the rate.4Legal Information Institute. UCC 3-112 Interest The principal has to be fixed; the interest can float.
Tools That Create a Sum Certain
Two devices in common commercial use are worth knowing because they turn messy claims into fixed ones.
An account stated is a snapshot of a running balance between parties who do business regularly. When a creditor sends a statement summarizing everything the debtor owes and the debtor fails to object within a reasonable time, courts treat the silence as agreement that the number is correct. What was once a tangle of individual charges becomes a single fixed debt, and the creditor can pursue it without having to prove each underlying transaction.
Liquidated damages clauses do the same job in advance. The parties agree at contract signing what the damages will be if one side breaches, which spares everyone from litigating actual losses later. For the clause to hold up, the figure has to be a reasonable forecast of the harm a breach would cause. A $500 per day late-delivery charge needs some tie to real costs like extra rental, inspection, or administrative expense. When the number tracks reality, courts enforce it. When it is wildly out of proportion, courts strike it down as a penalty. A workable liquidated damages clause gives you a sum certain the day the breach happens, which positions you to collect quickly through negotiation or the clerk-entry default judgment path.