If the only funds the left the old HSA during the year were those that were moved directly to the new HSA, no Form 1099-SA should have been issued and you should ask the old HSA custodian to correct the form to show $0 distributed, otherwise you would have to report it as a rollover as KrisD15 indicated. However, treating it as a rollover involves the one-rollover-per-12-months limitation. That limitation is not an issue if you did not roll over a distribution in the 12 months prior and will not do a rollover in the 12 months after, but you do not know what the future holds. You don't want to limit yourself by reporting a rollover on a transfer that was actually not a distribution and rollover. Also, if the new custodian properly treats it as a transfer and not a rollover, the new HSA custodian will not issue a Form 5498-SA that shows receipt of a rollover. The reporting of a distribution and rollover without the Form 5498-SA confirming receipt of a rollover could raise a red flag with the IRS.
