The IRS provides guidance on understanding your 227 Letter, acknowledgment letters sent to close an ESRP (Employer Shared Responsibility Payment) inquiry.

Document Excerpt

The various Letters 227 are acknowledgement letters sent to close an ESRP inquiry or provide the next steps to the Applicable Large Employer (ALE) regarding the proposed Employer Shared Responsibility Payment (ESRP). There are five different 227 letters:
Link

https://www.irs.gov/individuals/understanding-your-letter-227