Someone close to me has for years volunteered with a group that helps people prepare and file their tax returns for free. The effort is supported by the IRS. This year they started a pilot program where some of the volunteers are loaned IRS laptops with tax software so that the returns can be filed electronically. At the end of the tax season the laptops are to be returned to the IRS until the next tax season.
I don't know how they are currently securing the information on the laptops. Perhaps each return is deleted as soon as it has been sent. Even so, some risk would remain. This seems like an excellent application for Wave's software