What is a Schedule C clearance year?

According to Markaz, your Schedule-C Clearance Year is defined as the last continuous

(unbroken) Fiscal Year in which you have submitted a Schedule C without skipping any prior year.

Example:

If you submitted Schedule-C forms consistently up to Fiscal Year 2020 – 2021. You then skipped 2021–2022, and 2022–2023, but later submitted forms for FY 2023–24 and FY 2024–25. Despite submitting the most recent forms, your Clearance Year remains FY 2020 – 2021 due to the missing years in between.