Pre-Existing Duty
A rule that performing - or promising to perform - something one is already legally obligated to do cannot serve as valid consideration for a new contract.
While straightforward in theory, many businesses fail to actively track obligations tied to this concept - often resulting in missed deadlines, unintended renewals, penalties, or loss of contractual rights.
US Law · For business owners and foundersWhat is a Pre-Existing Duty?
The pre-existing duty rule provides that a promise to do - or actually doing - something that a party is already legally obligated to do cannot constitute valid consideration for a new contract or contract modification. Because consideration must be something of legal value that the promisor was not previously required to provide, an existing duty adds nothing new to the bargain.
The rule most commonly arises when a contractor, midway through a project, demands extra compensation to finish work already contracted for. Under the pre-existing duty rule, a promise to pay more for the same work lacks consideration - the contractor was already obligated to complete the project. The modification is unenforceable as a one-sided extraction.
Several exceptions have eroded the rule. Under UCC § 2-209, a modification to a contract for the sale of goods requires no consideration to be binding, provided it is made in good faith. The Restatement (Second) of Contracts § 89 allows enforcement of a modification if the circumstances were unanticipated when the contract was formed and the modification is fair and equitable. Courts also enforce modifications supported by new, independent consideration.
In practice, many teams rely on a contract expiry tracking system to stay on top of dates and obligations tied to clauses like this.
Key Elements
Existing Legal Obligation
The rule applies only where a legal duty already exists - not a moral obligation or social duty.No New Consideration
If the modification adds new obligations or modifies scope, new consideration exists and the rule does not apply.UCC § 2-209 Exception
For goods contracts, modifications are enforceable without new consideration if made in good faith. A "no oral modification" clause may still require the modification to be in writing.Unanticipated Circumstances
Courts may enforce a modification supported by genuinely unanticipated difficulties, even without new consideration, under the modern Restatement approach.Real-World Example
A builder is contracted to renovate an office for $150,000. Midway through, the builder demands $170,000 or will stop work. The owner, needing the space, agrees. The builder finishes. Can the owner later refuse to pay the extra $20,000?
Under the pre-existing duty rule, the owner's promise to pay $20,000 more for the same work lacks consideration - the builder was already obligated to complete the renovation. The modification is likely unenforceable, and the owner owes only the original $150,000. However, if genuinely unanticipated site conditions caused cost overruns, a court might enforce the modification under the Restatement exception.
This is why many businesses adopt automated deadline tracking to ensure no critical dates are missed before they pass.
Sample Clause Language
Contract Modification Clause (Protecting Against Pre-Existing Duty Issues)Watch Out For
Mid-project demands may be economically coerced modifications
A contractor's threat to stop mid-project to extract higher pay may also be challenged as economic duress - a separate doctrine that can void the modification regardless of the pre-existing duty rule.Always add new consideration when modifying contracts
When modifying a services contract, include something new - extended time, reduced scope, additional deliverables - to provide consideration for any increase in compensation. This ensures enforceability.Don't let pre-existing duty deadlines catch you off guard
Key dates tied to pre-existing dutys - renewal windows, expiry cutoffs, notice periods - can easily slip through the cracks when tracked manually. Missing them triggers automatic extensions, penalties, or lost rights. ExpiryEdge tracks every critical deadline and sends automated reminders before they're due - so nothing slips.
Instead of relying on spreadsheets or manual follow-ups, a centralized renewal reminder system ensures every deadline is visible, tracked, and actioned automatically.
How to Use This in Your Favor
Include a scope-change procedure in service contracts
A clear change order process - requiring written approval and pricing before additional work begins - prevents mid-project holdups and pre-existing duty disputes.Document unanticipated conditions immediately
If a contractor claims unexpected conditions justify a price increase, require contemporaneous documentation before agreeing to any modification. Documented unanticipated circumstances support enforceability under the Restatement exception.Frequently Asked Questions
Does the pre-existing duty rule apply to settlement agreements?
Settling a disputed (unliquidated) claim is generally not subject to the rule - giving up a good-faith legal claim is valid consideration. But promising to pay a debt you already undisputedly owe in exchange for a promised payment waiver may lack consideration.
Does the pre-existing duty rule apply under the UCC?
No - UCC § 2-209 eliminates the consideration requirement for modifications to goods contracts, provided the modification is made in good faith. However, a written "no oral modification" clause can still require written amendments.