Box 7 is the classification box. That code helps determine whether the amount is treated as a normal retirement withdrawal, an early distribution, a death benefit, a disability distribution, or a rollover. For many taxpayers, Box 7 answers the. Box 3 on Form 1099-SA contains a single-digit code that tells you and the IRS why money left your Health Savings Account, Archer Medical Savings Account, or Medicare Advantage MSA. These codes are essential for accurately reporting the distribution on the taxpayer's tax return and determining the appropriate tax treatment.