COB (Close of Business)
A deadline term meaning the end of normal business hours on a specified date; typically 5:00 PM in the recipient's time zone, though contracts should specify explicitly.
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 COB (Close of Business)?
COB (Close of Business) is a deadline term used in contracts and business communications to indicate the end of normal business hours on a specified date. While commonly understood as 5:00 PM or 17:00, the exact time varies by company and industry. Without explicit definition in the contract, "COB" can create ambiguity and disputes.
COB deadlines typically apply only to business days (Monday through Friday, excluding holidays). If a COB deadline falls on a weekend or holiday, the deadline automatically extends to the next business day. However, contracts should make this clear.
In multi-state or international transactions, COB creates timing disputes if the time zone is not specified. A contract saying "payment due COB" is ambiguous if one party is in New York and the other is in California. Always specify the time zone.
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
Explicit Time Definition
Rather than using COB, specify the exact time: "5:00 PM EST" or "17:00 Eastern Time." This eliminates ambiguity about what time the deadline falls on.Time Zone Designation
Always designate a time zone in COB clauses: "COB New York time" or "COB the recipient's local time zone." Without designation, disputes are likely.Business Day Clarification
Clarify whether COB applies only to business days (typical) or all days. Include language about what happens if the deadline falls on a weekend or holiday.Method of Delivery
COB deadlines may depend on delivery method: does "COB receipt" mean the recipient must receive the document by COB, or does it mean sent by COB? Specify.Notice of Extension
If a COB deadline is missed by seconds, either party may negotiate an extension. Include language about how extensions are requested and granted.Real-World Example
A contract requires a company in Chicago to submit a bid "by COB." The company is unsure whether this means 5:00 PM Chicago time or 5:00 PM in the buyer's office location (New York). The company submits the bid at 5:00 PM Chicago time (6:00 PM New York time) and the buyer rejects it as late.
The ambiguity about time zones created a dispute. A clear deadline like "5:00 PM EST" would have prevented this. The company should have asked for clarification before missing a potential deadline.
This is why many businesses adopt automated deadline tracking to ensure no critical dates are missed before they pass.
Sample Clause Language
Clear COB Deadline ClauseWatch Out For
COB Without Time Zone Is Ambiguous
Avoid saying just "COB" without specifying the time zone. This creates disputes, especially when parties are in different time zones.COB May Not Be 5:00 PM for Your Industry
Some industries or companies use different close-of-business times (e.g., 4:00 PM, 6:00 PM). Do not assume 5:00 PM is standard; verify with the other party.Electronic Delivery Timing Is Ambiguous
Does "COB submission" mean sent by COB or received by COB? Email can be delayed. Specify: "Submission shall be deemed timely if sent by COB, regardless of receipt time" or vice versa.Daylight Saving Time Changes Create Risk
On days when daylight saving time changes, times shift by one hour. If a deadline is 5:00 PM and clocks move forward, is the deadline 4:00 PM clock time or 5:00 PM actual time? Specify.Don't let cob (close of business) deadlines catch you off guard
Key dates tied to cob (close of business)s - 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
Always Specify Time Zone in COB Deadlines
In contracts with multi-state or international parties, always designate "COB [City] time" or "COB [Time Zone] time." This prevents disputes about timing.Use Specific Times Instead of COB
Instead of "COB," use "5:00 PM EST" or "17:00 Pacific Time." This is clearer and less subject to interpretation disputes than vague "close of business" language.Related Terms
Frequently Asked Questions
If the COB deadline is Friday at 5:00 PM, does that include Friday afternoon?
Yes. If you submit something Friday at 4:00 PM, you are within the deadline. If you submit Friday at 5:01 PM, you are late. COB means the very end of business hours.
What time zone should be used if not specified?
If the contract does not specify a time zone, the receiving party's time zone is typically assumed. However, this can be disputed. Always specify to avoid ambiguity.
Does COB apply on days the recipient's business is closed?
Not typically. COB is understood to apply on regular business days. If the deadline falls on a day the recipient is closed (holiday, weekend), it usually extends to the next business day. Specify this in the contract.