What it is
The 1095-C shows the months coverage was offered, the employee share of the premium, and the offer codes. IRS matching compares the W-2 affordability lines with the 1095-C months, and mid-year separation splits the record between two employers.
What to do about it: Keep the 1095-C from every employer in the year. Missing months create the reconciliation math, and the affordability codes drive the subsidy question.
Plain-language description of US practice, not legal, tax, or financial advice. The paired guide carries the citations, dates, and thresholds; the state pages carry the local windows.