Investing
The Wash Sale Rule Disallows A Loss You Really Took
Selling a security at a loss and reacquiring something substantially identical within a defined window defers the loss rather than allowing it, which surprises many investors.
An investor who sells a holding below cost has genuinely lost money. Federal rules nonetheless disallow claiming that loss if a substantially identical security is acquired within a set window around the sale.
The window runs both directions
The rule covers a period before and after the sale, not merely afterward. Buying shortly before selling can trigger it just as buying afterward does.
This catches investors who add to a position, then sell an older lot at a loss, without realizing the recent purchase falls inside the window.
The window is defined in days and counted around the trade date, which means the calendar rather than any intention determines whether the rule applies.
The loss is deferred, not destroyed
A disallowed loss is added to the cost basis of the replacement shares, and the holding period carries over as well.
When those replacement shares are eventually sold without a further triggering purchase, the deferred amount is recognized then.
The economic effect is therefore about timing rather than permanent forfeiture, which matters for planning even though it is frequently described as losing the deduction.
Substantially identical is the ambiguous term
Shares of the same company are clearly covered. Two index funds from different providers tracking the same index occupy far less settled ground.
The term is not exhaustively defined in a way that resolves every fund comparison, and reasonable interpretations differ among practitioners.
Options and convertible instruments on the same underlying can also fall within scope, which widens the rule beyond simple share repurchases.
Accounts other than the one that sold
The rule is applied to the taxpayer rather than the account, so a purchase in a different brokerage account can trigger it.
Purchases inside retirement accounts have been addressed by guidance in a way that is particularly unfavorable, since the basis adjustment has nowhere useful to go.
Automatic dividend reinvestment is a common unnoticed trigger, because it purchases shares on a schedule the investor is not actively watching.
Why brokerage reporting is incomplete
Brokers report wash sales on the forms they issue, but only within the accounts they hold and only for identical securities as they classify them.
An investor holding accounts at several firms, or a spouse holding a related position, can have adjustments the reporting does not capture.
Because the rules are technical, apply differently to different instruments, and are revised over time, an investor harvesting losses at scale should work with a tax professional.
Questions readers ask
Does this mean I should sell before a fall?
Only if you can identify falls in advance, which the evidence suggests almost nobody does consistently. The practical response is choosing an allocation whose falls you can sit through.
Why do average returns overstate what I got?
Because averaging percentages ignores that each return applies to a different balance. The compound return accounts for that and is always lower when returns vary.
