The 30-Day Window Explained
The 30-Day Window Explained
The wash-sale rule is mechanical and unforgiving. If you sell at a loss on Day 0, you cannot repurchase the same security between Day -30 and Day +30. That is a 61-calendar-day window, not trading days. Weekends and holidays count. Even one day early triggers the disallowance. This section clarifies the exact mechanics so you do not make an error.
Key takeaways
- The 30-day window spans 61 calendar days: 30 days before the sale, the sale date itself, and 30 days after.
- Calendar days are counted, not trading days; weekends and holidays are included in the 30-day count.
- The safe date to repurchase is day 31 after the sale, not day 30.
- Multiple sales within the 30-day window extend the disallowance.
- Tracking this correctly requires a calendar and discipline; it is easy to miscalculate by one or two days.
How the window is calculated
If you sell a security on September 15 (the "sale date"), the wash-sale window encompasses:
- Days before: August 16 through September 14 (30 days prior to sale date)
- Sale date: September 15
- Days after: September 16 through October 15 (30 days after sale date)
Total: August 16 through October 15.
You cannot repurchase the same security anytime during this period. The first safe date to repurchase is October 16.
Let's verify the count:
- August 16–31: 16 days
- September 1–15: 15 days (includes sale date)
- September 16–30: 15 days
- October 1–15: 15 days
- Total: 61 days
October 16 is day 62 and is outside the window.
Calendar days, not trading days
A common mistake is thinking the 30-day period resets on the next trading day after 30 calendar days have passed. It does not. If you sell on September 15 (a Friday) and count 30 trading days forward (which lands on about October 27), you might think you can repurchase on October 27. You cannot. The rule uses calendar days.
In the example above, the safe date is October 16, regardless of what day of the week it falls on. If October 16 is a Saturday, you can repurchase on the next trading day (Monday, October 18) without triggering the rule.
Weekends and market holidays are included in the 30-day count.
Multiple sales in quick succession
If you sell the same security multiple times within a 30-day window (a rare scenario), the wash-sale clock resets with each sale.
Example: You sell VTI on September 1 at a loss. On September 10, you sell more VTI at another loss. You cannot repurchase either lot until October 10 (30 days after the September 10 sale, which is the later of the two). The September 1 sale is superseded by the September 10 sale; they merge into a single wash-sale window.
The 61st day rule: when you can safely repurchase
Because the window is 61 days (not 60), the safe repurchase date is day 61 + 1 = day 62 after the sale. For a September 15 sale, that is October 16.
Some investors remember "the 31st day after the sale," which is a shorthand that also works: September 15 + 31 days = October 16.
To avoid errors, use a calendar or spreadsheet:
| Scenario | Sale Date | Day 31 After Sale | Day 61 After Sale | Safe Repurchase Date |
|---|---|---|---|---|
| January sale | Jan 15 | Feb 15 | Mar 15 | Mar 16 |
| September sale | Sep 15 | Oct 15 | Nov 14 | Nov 15 |
| December sale | Dec 15 | Jan 15 | Feb 13 | Feb 14 |
Note: In leap years (2024, 2028, etc.), February has 29 days, which shifts the dates slightly.
Potential off-by-one errors and how to avoid them
Off-by-one errors are common:
-
Counting the sale date as day 1 of the 30-day window: Incorrect. The sale date is day 0. Day 1 is the trading day after sale. The 30-day window ends 30 days after the sale, not including the sale itself.
-
Repurchasing on day 30 instead of day 31: Incorrect. Day 30 is still within the window. Day 31 is safe (for the "day 31" rule), but the safest approach is to wait until day 62 to avoid confusion.
-
Assuming "one month later" is sufficient: Incorrect. October 15 is one month after September 15, but it is not safe to repurchase on October 15 (still within the window). October 16 is safe.
To prevent errors, write down the safe repurchase date immediately after selling. For a September 15 sale, write "Safe to repurchase on October 16 or later." Refer to this note when tempted to repurchase.
Brokers and wash-sale tracking
Most brokers track the 30-day window automatically and will warn you if you attempt to repurchase a security within the window. However, broker tracking is not foolproof, especially if you hold accounts at multiple brokers or in spouse accounts. Ultimately, you are responsible for compliance.
Some brokers allow you to set a reminder or flag for wash-sale dates. Take advantage of these features if available.
Wash-sale window calendar
Related concepts
Next
The 30-day rule applies to taxable brokerage accounts. But many investors hold positions in 401(k)s, IRAs, and other tax-deferred plans. Can you harvest losses in these accounts? The short answer is no, and understanding why is critical to avoiding wasted effort.