A long stop date is the contractual deadline by which a signed deal must close, after which either party (or sometimes both) can walk away from the agreement. It appears in merger, acquisition, and large real estate contracts where regulatory approvals, financing, and third-party consents sit between signing and closing. Without it, a buyer or seller could stay bound to a deal indefinitely while waiting on approvals that may never come.
How the Clock Works
Signing the purchase or merger agreement creates binding obligations, but closing doesn’t happen until the conditions in the contract are satisfied: regulatory clearance, shareholder approval, third-party consents, financing. The long stop date puts an outer boundary on that process. If every condition is met before the date arrives, the parties close and the date never matters. If conditions are still outstanding when the clock runs out, the agreement either expires on its own terms or gives one or both parties the right to terminate.
The point is to keep capital committed only for a defined window. Sellers know they won’t sit indefinitely with a buyer who can’t close. Buyers know they won’t watch a target deteriorate for years while regulators deliberate. Both sides plan around a fixed calendar date rather than an open-ended “whenever.”
Why the Gap Between Signing and Closing Exists
The length of the long stop date is driven by the conditions that have to be cleared before closing. A handful of approvals do most of the work.
Antitrust Review Under Hart-Scott-Rodino
The Hart-Scott-Rodino Act requires parties to notify federal antitrust regulators before completing transactions above certain dollar thresholds. For 2026, a filing is required when the deal’s size reaches $133.9 million, with additional thresholds based on the size of the parties.1Federal Trade Commission. FTC Announces 2026 Update of Jurisdictional and Fee Thresholds for Premerger Notification Filings After filing, the parties must wait 30 days before closing (15 days for cash tender offers). If regulators issue a “second request” for more documents, the clock resets for another 30 days once both sides have fully complied.2Office of the Law Revision Counsel. 15 U.S. Code 18a – Premerger Notification and Waiting Period Second requests are where timelines balloon; producing the required documents can take months.
Foreign Investment Review
Transactions involving foreign buyers may trigger review by the Committee on Foreign Investment in the United States. CFIUS examines whether a deal threatens national security, and certain transactions involving foreign government acquirers or critical technologies require a mandatory filing.3U.S. Department of the Treasury. CFIUS Overview The statutory timeline allows 45 days for an initial review, a further 45-day investigation if needed, and a final 15-day window for a presidential decision in the most sensitive cases.4Office of the Law Revision Counsel. 50 USC 4565 – Authority to Review Certain Mergers, Acquisitions, and Takeovers That is up to 105 days of regulatory process on top of whatever preparation time the parties need.
Shareholder Votes and Third-Party Consents
Public company mergers almost always require a shareholder vote, which means drafting a proxy statement, filing it with the SEC, waiting for review and comments, mailing the final version, and holding the meeting. That alone can take two to four months. A deal may also need lender or landlord consents under change-of-control clauses, environmental permits, or final financing commitments. Each layer adds time the parties must build into the long stop date.
What the Parties Must Do While the Clock Runs
Signing doesn’t freeze the deal in place. Both sides pick up obligations that govern how they behave until closing or termination, and those obligations shape who can later invoke the long stop date.
Interim Operating Covenants
The seller (or target company) typically agrees to run the business in the “ordinary course” between signing and closing. No large acquisitions, no unusual dividends, no firing key executives, no major new contracts, no loading up on debt. The buyer is paying for the business as it exists at signing, and these covenants stop the seller from changing what the buyer is getting. Anything outside the ordinary pattern usually needs the buyer’s written consent, often above a negotiated materiality threshold.
Effort Standards for Clearing Conditions
The contract also specifies how hard each side must work to satisfy the closing conditions. “Best efforts” is the most demanding standard and can require a party to pursue regulatory approval even at significant financial cost. “Commercially reasonable efforts” is more forgiving, letting a party weigh its own business interests. “Reasonable efforts” falls somewhere between, though some courts treat it as interchangeable with one of the others.
The standard chosen matters when the date arrives with conditions still open. A buyer who agreed to use best efforts to obtain antitrust clearance has far less room to drag its feet than one who committed only to commercially reasonable efforts. If one side argues the other didn’t try hard enough, the effort standard is the yardstick.
Setting and Extending the Date
Most M&A long stop dates land somewhere between three and twelve months after signing, depending on regulatory complexity. A domestic deal with no antitrust concerns might sit in the three- to six-month range. A cross-border acquisition requiring CFIUS review, European Commission clearance, and multiple country-level filings could justify twelve months or longer. The parties estimate the longest plausible regulatory timeline, add a buffer for second requests and complications, and negotiate from there.
Many agreements include built-in extension provisions so the deal doesn’t automatically die if one approval is still pending when the original date hits. A common approach gives one or both parties the right to extend the long stop date by a fixed period, often three to six months, when the only unsatisfied condition is regulatory clearance. Some extensions kick in automatically; others require mutual consent or a written election. A central negotiating point is whether the extension right belongs to both parties or only to the one that isn’t responsible for the delay.
What Happens When the Long Stop Date Passes
If conditions remain unfulfilled when the date arrives, the termination provisions take over. The mechanics depend on how the agreement is drafted.
Automatic Versus Elective Termination
Under automatic termination, the agreement expires on its own when the date passes. Under elective termination, one or both parties gain the right to end the deal by written notice, but the contract stays alive until someone exercises that right. Most practitioners prefer elective termination. If the last regulatory approval arrives two days after the long stop date, an elective structure lets the parties close anyway rather than losing the deal to a technicality.
You Cannot Terminate If You Caused the Delay
Nearly every well-drafted agreement bars a party from terminating if its own breach caused the failure to close. A buyer who deliberately slow-walked its antitrust filing cannot invoke the long stop date to escape a deal it no longer wants. The right to terminate belongs to the party that held up its end. This is where the effort standards do their real work: whether a party’s conduct counts as a breach often turns on whether it met its commercially reasonable efforts or best efforts obligation.
Deposits, Fees, and Financial Unwinding
When the deal terminates, escrowed funds have to be returned or allocated. In M&A transactions, the unwinding usually runs through break-up fees (paid by the target, typically triggered when the target’s board switches to a competing offer) or reverse termination fees (paid by the buyer, typically when antitrust approval fails). In real estate, the buyer’s earnest money deposit is the asset at stake. If termination follows a legitimate condition failure like denied financing or a zoning variance that never came through, the deposit typically returns to the buyer. If the buyer walked away or caused the delay, the seller may keep it as liquidated damages.
Tax treatment of a retained deposit catches some parties off guard. A seller who keeps a forfeited deposit generally reports it as ordinary income rather than capital gain, because the money represents damages for a failed transaction rather than proceeds from a completed sale. For the party whose contractual right was terminated, gains or losses from the cancellation of a right related to a capital asset may qualify for capital gain or loss treatment.5Office of the Law Revision Counsel. 26 U.S. Code 1234A – Gains or Losses From Certain Terminations
A Separate Exit: The Material Adverse Change Clause
The long stop date isn’t the only way out of a signed deal, and the two mechanisms shouldn’t be confused. Most agreements also include a material adverse change clause that lets the buyer terminate before the date if the target’s business suffers a serious downturn between signing and closing: a factory burns down, a key product fails a regulatory test, revenue collapses.
The two interact. If the buyer invokes a MAC clause, the seller will often dispute whether the change was truly material and adverse, and while that fight plays out, the long stop date keeps ticking. If the buyer’s MAC claim ultimately fails, the buyer may have lost its window to close, and the seller may gain the right to terminate instead. The long stop date is the time-based exit; the MAC clause is the event-based exit. A party weighing whether to walk away has to look at both.