I had a capital gain from a mutual fund. I did not sell it was a distribution. The shares at distribution were $87.22. My average cost is $38.61 Can I deduct and how?

If you had a capital gain distribution on your 1099-DIV you report the amount on that form. The gain was incurred by the fund itself and passed on to you. 

Please clarify. What tax form did you receive, Form 1099-DIV or Form 1099-B?

I got a 1099 DIV.

So do I need to pay taxes on the entire capital gain?

Yes but it gets taxed at lower capital gains rate.  You didn't sell any of your shares.  The fund just passed on internal gains to you.  

Oh I didn't see it was such a large amount.  Which fund?   There was another post earlier in the year about a fund that did that.  Something had happened that wasn't planned or the fund accounting was wrong.   Don't know if I can find it.  Maybe if you post the company name or fund.  They might have a footnote or statement with your 1099Div.   

American Century Ultra. Capital gain distributions are normal but usually not this much. 

There is no alert on their site for any discrepancies on the statements issued.  You can use the link below to review the information for your fund or contact your financial advisor to review your activity. As noted by our Tax Champ @VolvoGirl the capital gains distributions are taxed at a lower rate.

• The tax rate on most net capital gain is no higher than 15% for most individuals. Some or all net capital gain may be taxed at 0% if your taxable income is less than or equal to $40,400 for single or $80,800 for married filing jointly or qualifying widow(er). 

• A capital gain rate of 15% applies if your taxable income is more than $40,400 but less than or equal to $445,850 for single; more than $80,800 but less than or equal to $501,600 for married filing jointly or qualifying widow(er); more than $54,100 but less than or equal to $473,750 for head of household or more than $40,400 but less than or equal to $250,800 for married filing separately.

  However, a net capital gain tax rate of 20% applies to the extent that your taxable income exceeds the thresholds set for the 15% capital gain rate.

Why are some distributions larger than others? (Per American Century Ultra)

The amount of a distribution can increase when the dividend payments or profits increase. A fund's capital gain distribution, however, is not necessarily a reflection of its overall performance. Because regulations regarding distributions are complex, you may want to consult a tax advisor about your circumstances.

American Century Investments® pays per-share distributions to shareholders invested on the fund's record day. On the Payable Date, each fund's share price is reduced by the amount of its distribution. If distributions are paid to your account, you will see them on your fourth quarter statement and for taxable accounts in taxable funds, on the IRS Form 1099-DIV you will receive.

My real question is do I have to pay taxes on the entire capital gain. My costs using dollar cost averaging are about  $15,000 and the capital gain distribution is about $34,000. Shouldn't I be able to subtract the $15,000 from the $34,000 and pay taxes on just the $19,000?

If you can confirm with the payer that this was a payment intended to be a return of capital then it could be considered a 'Nondividend Distribution'.  A nondividend distribution is nontaxable because it is a return of capital.  Also, this amount should be in Box 3, Form 1099-DIV. Talk to the company and inquire about this detail.

That being said, if this is not on your dividend statement or documents from the merger clearly identifying this as a return of capital, then you will pay tax on the qualified dividends under the capital gain tax rules.

@tc8751