You may not receive a W-2 because you are no longer an employee but a retiree. You should receive a form 1099R that, if reported accurately will account for all benefits received. You will need to enter that for form 1099R as received.
Generally, contributions made by an employer to the health savings account (HSA) of an eligible employee are excludable from an employee's income and are not subject to federal income tax, Social Security or Medicare taxes.
Use this IRS link for additional information.
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