From Labor Attorney Jason Cogdill:

I have received many reports about employers receiving notices from the Marketplace since the middle of last week.  These are “1411 Certifications” from HHS identifying individuals currently receiving an advanced premium credit (or cost-sharing reduction) and whose application referenced a specific employer.  It is likely that the majority of employers will receive at least one of these notices, so if your clients have not communicated to you about the notices, they soon will.