He found that we were not but that our landlord lacked a valid certificate of occupancy.

Without a valid certificate, you may find it hard to get a mortgage or to resell to someone who needs one.

One can create a valid signature without using a valid certificate and add it to the list.

Evidence was given that the aircraft had a valid certificate of airworthiness and that at the time of the accident it was operating in an unmodified form.

A further 991 empty homes do not have valid certificates.