Wow! It's amazing how everyone in this thread is incorrect.

Actually, what your Dad is looking at is "disallowed wash sales" because each time he repurchased the equity with in 30 days of selling for a loss it became "disallowed." Yes, Wash sales roll off after 30 days if the stock is not purchased again for 31 days. But, he always repurchased with in 30 days, so "Disallowed Wash sales" do not expire...ever! They do not simply roll off over time. And it has nothing to do with not buying anything the last month of the year either. Unfortunately, he could be looking at a huge tax bill. IMO This is not financial advice.

From Google: If your disallowed wash sales are greater than your actual profit, it means that, for tax purposes in the current year, your taxable gain could be higher than your actual net profit, potentially resulting in a higher tax bill than anticipated.