A computer program product comprising a non-transitory computer readable storage medium embodying one or more instructions executable by a computer system having a server computing device and a tax return preparation computing device to perform a process for masking tax data during collaborative preparation of an electronic tax return using a system including a server computer, a tax return preparation computer, and a support computer operatively coupled by a network, the process comprising a first browser running on the tax return preparation computer, the first browser being used by a user to enter data into the tax return preparation program and being adapted to identify if data entered by the user comprises a tax datum for the tax return preparation program comprising sensitive data and automatically mask the tax datum when the tax datum is identified as comprising sensitive data, without user intervention and before transmitting the tax datum to the server computer for subsequent transmission to the support computer, the tax datum being masked in real time during collaborative preparation of the electronic tax return such that sensitive data is not transmitted to the support computer or displayed by a second browser program operating on the support computer.