Thank you for your inquiry regarding CMS22v12 Preventive Care and Screening: Screening for High Blood Pressure and Follow-Up Documented. The encounter start date/time should reflect the earliest point of arrival for a patient to the healthcare setting. This may not be universally captured in a single field across all providers, as you are noting, and should be site-specific mapping. If the site captures check in as the earliest point of arrival, then that should be aligned at their site across all implemented measures. If registration reflects the earliest point of arrival, then that should be used at respective sites. Registration is typically an administrative time, and triage of a patient can occur prior to administrative paperwork completion.