What must Sandeep and Mary do since their combined gross income is $28,400?

Sandeep and Mary are required to file a tax return because their combined gross income exceeds the filing threshold set by the IRS for the tax year. The filing threshold varies depending on factors such as filing status, age, and whether the taxpayer is blind, but generally, for most taxpayers, if their gross income exceeds a certain limit, filing a tax return becomes mandatory.

In this scenario, since their combined gross income is $28,400, it surpasses the threshold for most filing statuses, meaning they must file a return to fulfill their legal obligations. Filing a tax return not only ensures compliance with tax laws but also allows them to accurately report their income and potentially qualify for deductions or credits that could lower their tax liability.

Other options, while they may touch on different aspects of filing, do not address the mandatory requirement based on their income level. For example, claiming a refund might be relevant if they had withholding or estimated tax payments exceeding their liability, but it does not negate the primary requirement to file due to their income.