Legal Question in Real Estate Law in Illinois

Insufficient information. That being said, it may depend on what kind of notice was served. If it was for non-payment of rent under Illinois statutes, it SHOULD say your tenancy or lease is terminated after 5 days after service of the notice. While that technically terminates the lease and therefore technically makes it no longer "valid" the landlord still has to file an eviction lawsuit to "perfect" his rights to have you dispossessed. So take the notice to an attorney for proper analysis. You may have defenses that could "re-validate" the lease or knock out the notice, which may also have the effect of revalidating your lease.