Please note that Betterment is not a tax advisor and the information provided should not be construed as tax advice, but should be used for informational purposes only. Please consult a qualified tax professional or the IRS to determine the rules that apply to your individual tax situation.
For the purposes of reporting your Betterment transactions by filing Form 8453, you should check "Form 8949, Sales and Other Dispositions of Capital Assets (or a statement with the same information), if you elect not to report your transactions electronically on Form 8949" when completing Form 8453.
Certain versions of tax preparation software have a limit on the number of transaction lines they support for automatic upload. This varies from provider to provider. If you are unable to automatically import your tax forms into your tax software, the IRS allows you to report the summary information on your electronic tax return and send a paper copy of your statement with Form 8453 to the IRS after your tax return has been accepted.
For more information about Form 8453, please see www.irs.gov/uac/About-Form-8453.