In accordance with IRS regulations, you can use the TurboTax software to e-file up to five (5) federal tax returns. You can prepare as many returns as you want, but only five can be e-filed.
For returns with multiple states, you can e-file up to three (3) states per federal return; the rest must be paper-filed (which probably isn't a big deal, as many nonresident state returns can't be e-filed anyway).
Our license agreement doesn't allow the use of TurboTax for commercial or professional tax preparation. If you need to e-file multiple returns and you are a professional tax preparer, take a look at our ProSeries or Lacerte software.