How do I calculate cost basis for Old Mutual Funds?
Sophia Koch
Updated on April 10, 2026
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Also, how do I find the cost basis of an old mutual fund?
To calculate average basis:
- Add up the cost of all the shares you own in the mutual fund.
- Divide that result by the total number of shares you own. This gives you your average per share.
- Multiply the average per share by the number of shares sold.
Additionally, what is the best cost basis method for mutual funds? FIFO (First-in, First-out) is the default cost basis method used by most brokerages when you open a new account. That doesn't mean it's the best method to use every time. FIFO sells the oldest shares you own first. Because of this, it tends toward selling the longer-term tax lots.
Just so, how do you calculate cost basis?
You can calculate your cost basis per share in two ways: Take the original investment amount ($10,000) and divide it by the new number of shares you hold (2,000 shares) to arrive at the new per-share cost basis ($10,000/2,000 = $5).
How do I calculate cost basis for reinvested dividends?
With the single-category method, you add up your total investment in the fund (including all those bits and pieces of reinvested dividends), divide it by the number of shares you own, and voila, you know the average basis. That's the figure you use to calculate gain or loss on sale.
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