Can a commercial lease automatically renew without your knowledge?

Yes, in many jurisdictions a commercial lease can auto-renew at the end of its term if neither party gives notice to end it. The Landlord and Tenant Act 1954 in England and Wales gives business tenants a statutory right of renewal (the tenancy continues on the same terms until the parties agree new ones or the court is asked to determine them) -- but this isn't the same as a contractual auto-renewal, and tenants must actively engage to either renew or end the tenancy.

Contractual auto-renewal clauses are also common in commercial leases, especially for equipment leases. These explicitly state that the lease renews for a further term (often the original term, at the same or an updated rent) unless written notice is served before a specified deadline. The notice deadline can be 3-12 months before the end of the term -- miss it, and you're in for another full term.

Checking each lease individually for auto-renewal provisions and noting the notice deadline is the only reliable way to avoid being locked into a lease you've already mentally vacated.