What if I purchased a managed target date fund for my IRA by mistake instead of a target date index fund?

I recently rolled a six figure employer 401k into an IRA and purchased a managed target date fund. I had intended to purchase the equivalent target date index fund, which has a substantially smaller expense ratio. In the several months since the account has grown about $10k. What's my best move to correct this?

Moving investments within an IRA has no tax impact. You can buy and sell individual stock, or funds, or bonds. When your investments produce interest or dividends, there is no tax impact.

Only when you move funds out of an IRA to a Roth IRA, or a taxable account, is there a tax and/or penalty involved.

One of the best parts of the retirement account is the ability to re-balance with zero tax impact.

My understanding is that I'd pay short-term capital gains on the $10k if I sold and purchased the index fund, and I'd need to weigh that against keeping the managed fund for a year to reduce tax. Is it that simple? The fund is listed as "no load" and "no fee" at my broker.

Now depending on the rules of the funds there can be fees and loads, but it appears that the funds you are working with don't have any. There should be zero cost when selling the first fund and buying the second fund.