How to calculate lease notice deadlines

Published 6 October 2026. Updated 6 October 2026.

The problem with "180 days before expiry"

Many of the most expensive dates in a commercial lease are not written as dates. The lease says that the tenant may renew by giving notice "not less than 180 days before expiry", or that a break right needs "nine months' prior written notice". You have to turn that sentence into a date on a calendar, and small errors in the count can mean a right is lost.

This guide goes through the choices that change the answer. It describes general practice. Your lease controls, so read the exact words, and where a right hangs on one day, check with your attorney.

Step 1: Find the anchor date

Every notice period is counted from or back to an anchor. Typical anchors are the expiry date, the break date, the end of a rent-free period, or a date a previous notice was received. Write the anchor down first, and note which document sets it. If an amendment changed the expiry, the old expiry is the wrong anchor.

Step 2: Identify the unit

Read the unit carefully. These are not the same:

• Calendar days count every day, including weekends and holidays.
• Business days skip weekends and, usually, holidays. The lease may define which holidays count.
• Months run from a date to the same date in a later month, which causes the month-end problem described below.

A period written as "180 days" is normally read as calendar days unless the lease says otherwise. A period written as "six months" is not the same as 180 days: six calendar months run 181 to 184 days, so the two answers can be several days apart.

Step 3: Decide whether the first day counts

Some leases say whether the day notice is given counts, many do not. Phrases such as "not less than" or "at least" are sometimes read as "clear days": the whole period must fall between the day notice is given and the anchor date, with neither day counted. That reading moves the deadline one day earlier than simple subtraction. The difference is a single day, which is exactly the size of error that loses a right. Where the lease is silent, the cautious practice is to work out both answers and plan to the earlier one.

Step 4: Count back, then handle the weekend

Work out the raw date. Then ask what the lease says if that date is a weekend or holiday. Three outcomes are common:

1. The deadline moves to the next business day.
2. The deadline moves to the previous business day.
3. The lease is silent.

Some state laws move certain deadlines that fall on a weekend or holiday, but whether one applies to your lease is a question for your attorney. As a matter of practice, when the lease is silent, plan to send notice by the business day before. Losing a right by a day because you hoped the date would roll forward is a poor trade.

Step 5: Watch for month ends and leap years

Month arithmetic breaks at the end of a month. If a lease starts on 31 January and the first rent adjustment is one month later, there is no 31 February. The usual reading puts the date on the last day of February, which is 28 or 29 depending on the year. A lease that commences on 29 February has the same problem in every year without a 29 February: one reading takes 28 February, another takes 1 March.

Check any date that is computed from a 29th, 30th or 31st, and read the lease to see if it states a rule for short months. If it does not, record what rule you applied.

Step 6: Apply the amendment

An amendment can change the length of a notice period, the anchor date, or both. For example, an amendment may shorten a renewal notice from 180 days to 90. The deadline then moves 90 days later, and the clause in the base lease no longer governs. Always confirm that you are counting with the amended clause.

Step 7: Allow time for delivery

Finding the deadline is half the job. The notices clause says how notice must be given, to whom, and when it is treated as received. If notice must be received by the deadline, a courier or post that takes three days means you must send it earlier. Record a send-by date as well as a deadline.

Worked examples to test your own count

These are invented leases with simple clauses, to practise the method.

Count each one yourself first, then compare. If your answer differs, check whether you counted the first day and whether you used calendar days.

A checklist before you trust a date

• The anchor date comes from the governing document.
• The unit is clear: calendar days, business days or months.
• You know whether the first day counts.
• You have checked weekend and holiday handling.
• Month ends and leap days are handled and noted.
• Amendments are applied.
• A send-by date allows for delivery.
• The date is recorded with its working, so it can be audited. For a wider tracking method, see our guide to tracking commercial lease critical dates.

How LeaseDeadline does this step

In LeaseDeadline the AI model reads the lease, but ordinary code does the date arithmetic, so each date shows its working, for example "not later than 180 days before 2027-04-30 = 2026-11-01". A period stated in days is counted back in calendar days and one stated in months by calendar month; when a month has no matching day, the date falls on that month's last day. The code does not move a deadline that lands on a weekend or holiday, and it does not count business days or clear days, so check those clauses against the lease yourself. A second AI model then reviews each date against the clause, and any amendment overrides the clause it changes, with the abstract citing the amendment.

Every date is listed with its page and clause so you can check the working. When the lease is unclear, the item comes back to you as a question. The result is model output, not legal advice, and the lease governs, so confirm any notice with your attorney. You can sign up to run a lease through it; an abstraction is 25 credits a lease.

Questions

What if a notice deadline falls on a weekend or holiday?

Leases handle this differently. Some push the date to the next business day, some to the previous one, and some say nothing. Do not rely on a shift that the lease does not state. If it is silent, plan to send notice by the business day before.

Does the day the notice is sent count as day one?

It depends on the wording and on local law. Phrases such as 'not less than' and 'at least' are sometimes read to mean the whole period must fall between the notice day and the anchor date, which moves the deadline a day earlier. If the count decides whether a right survives, ask your attorney.

Does notice have to be received, or only sent?

Leases often set out how notice is given and when it counts as delivered. Check the notices clause for the address, the method and the deemed delivery rule, and allow time for the method you choose.