ILR eligibility calculation

Hi All,
I have applied skilled worker visa from India during Sep 2021. My visa start date is 18th September 2021 and my UK entry date is 13th October 2021. There is a gap of 25 days between visa start date and entry date. I understand from home office portal that ILR application can be submitted up to 28 days before completing the qualifying period and based on that earliest application date should be 21st August 2026. Since there is 25 days gap between visa start date and entry date, my employer says the earliest application date is 15th September 2026. Please advise what would be my earliest application date( 21st August or 15th September)

The 28-day concession is NOT about when you apply at all. Your date of entry is irrelevant. You should NOT take immigration advice from your employer.

Your earliest date of ILR eligibility is 18th September 2021 + 5 years - 28 days

READ: All you need to know about applying early, the application date, 28-day concession and more