A proposal, not the bill
Letter 226-J tells an applicable large employer that it may owe an Employer Shared Responsibility Payment under the Affordable Care Act. The IRS uses employer reporting and employee return information to calculate the proposal.
Reconcile the underlying records
Check the tax year, Forms 1094-C and 1095-C, and the employee information supplied with the letter. Use Form 14764 to respond. If you disagree, explain the errors and identify needed changes on Form 14765, with supporting records.
Use the response date printed on the letter. Ask the contact listed in it about additional time if needed; do not assume a request automatically extends the deadline.
Keep the response traceable
Organize your explanation by employee and month so another reviewer can follow it. Keep the letter, submitted forms, supporting records, and delivery evidence together. A later Letter 227 communicates the outcome or next steps; CP220J is the billing notice after assessment.