We have a prepared schedule H from the company we use to handle our household employment payments, so we could enter the figures manually if we could figure out how to directly access schedule H on TurboTax.
After you finish entering your information in the Nanny Tax section, go to Deductions & Credits >> Estimates and Other Taxes Paid >> Estimates.
The easiest way to find this section of TurboTax is to use the Search box at the top right side of the TurboTax header. Click on the magnifying glass, type in "estimated taxes paid", and hit Enter. The first result should be "jump to estimated taxes paid". Click on this link to go directly to the input screen for this topic.
Report the withholding taxes you paid quarterly for your household employee under Federal estimated taxes for 20XX (Form 1040ES). This includes Social Security, Medicare, and Federal income tax withholding.