Although Coinbase cannot provide legal or tax advice, the IRS has released guidelines for how to report taxes relating to digital currency activity. You can read them on the official IRS.gov website here: http://www.irs.gov/pub/irs-drop/n-14-21.pdf
With the exception of some business accounts, Coinbase does not provide 1099 forms.
Coinbase does however provide a specialized Cost Basis for Taxes report which will help with filing your taxes.
This report provides a summary of your digital currency purchases and sales, showing your cost basis and capital gain/loss.
We use a FIFO (first in first out) method for this report. Transactions sending into or out of your Coinbase wallet are treated as buys or sells at the current market price in this report. However, you should keep your own records for best results and update the report accordingly. For example, if you transfer funds offsite to a desktop wallet, and then back again, you would not count this as a sale of digital currency.
You can generate the report here, by clicking on "New Report" in the upper right hand corner.
This report is still in beta and should be used with caution.
Note that if you have any deleted digital currency wallets within your Coinbase account, they will not appear in the report generation tool. To restore them, navigate to your accounts page, select "Show Deleted" at the bottom, and then un-delete the wallet you'd like to run a report on.
Disclaimer: This report does not constitute legal or tax advice. Tax laws and regulations change frequently, and their application can vary widely based on the specific facts and circumstances involved. You are responsible for consulting with your own professional tax advisors concerning specific tax circumstances for your business. Coinbase disclaims any responsibility for the accuracy or adequacy of any positions taken by you in your tax returns.