In most commercial property leases, rent is reviewed periodically to an open market rent level. The hypothetical lease terms are the basis of valuation under a rent review clause which will prescribe the exact terms to be assumed and matters to be disregarded, in a hypothetical letting of the property at the review. They are usually based on the terms of the actual lease, but can vary, e.g. length of terms, break options included/excluded, assumptions as to permitted user etc…