Wash Sale Rules for Traders: Multi-Broker Aggregation and Disallowances

The wash sale rule is one of the most misunderstood tax provisions affecting active traders. Understanding how it works across multiple brokers is essential for accurate tax reporting.

What is a Wash Sale?

A wash sale occurs when you sell a security at a loss and purchase a substantially identical security within 30 days before or after the sale. The 61-day window includes 30 days before, the day of sale, and 30 days after.

The Multi-Broker Problem

Here's where it gets tricky: wash sale rules apply across ALL your accounts, not just within a single broker. If you sell Stock XYZ at a loss in your TD Ameritrade account and buy it back in your Interactive Brokers account within the 61-day window, it's still a wash sale.

What Happens to the Disallowed Loss?

The disallowed loss isn't lost forever—it's added to the cost basis of the replacement shares:

Broker Reporting Limitations

Individual brokers only track wash sales within their own platform. They have no visibility into your other accounts, so their 1099-B may understate your wash sale disallowances.

How to Handle Multi-Broker Wash Sales

1. Use specialized trading tax software that aggregates across brokers

2. Manually track purchases across all accounts

3. Adjust your 1099-B figures when filing Form 8949

The Mark-to-Market Solution

Traders who qualify for Trader Tax Status can elect Section 475 mark-to-market accounting, which eliminates wash sale rules entirely. This election must be made by the due date of your prior year return.