It is going to depend on whether your fund purchase are being tracked as FIFO or "average cost".
If FIFO you have to look at your records to see how many shares are "at a loss".
See Pub 550 for how to inform your fund custodian or broker that you want to use "average cost" before you take action.
OR
wait thirty one days before you do your repurchase of the security.
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Shares bought one year or less before your SELL ALL SHARES are Short Term and have to be reported separately (Form 8949 Pg 1).
@Anonymous
