Revenue Recognition and Accounts Receivable Our leases with tenants are classified as operating leases. Substantially all such leases contain fixed rent escalations which occur at specified times during the term of the lease. Base rents are recognized on a straight-line basis from when the tenant controls the space through the term of the related lease, net of valuation adjustments, based on management's assessment of credit, collection and other business risks. When we determine that we are the owner of tenant improvements and the tenant has reimbursed us for a portion or all of the tenant improvement costs, we consider the amount paid to be additional rent, which is recognized on a straight-line basis over the term of the related lease. For first generation tenants, in instances in which we fund tenant improvements and the improvements are deemed to be owned by us, revenue recognition will commence when the improvements are substantially completed and possession or control of the space is turned over to the tenant. When we determine that the tenant is the owner of tenant improvements, tenant allowances are recorded as lease incentives and we commence revenue recognition and lease incentive amortization when possession or control of the space is turned over to the tenant for tenant work to begin. Percentage rents, which represent additional rents based upon the level of sales achieved by certain tenants, are recognized at the end of the lease year or earlier if we have determined the required sales level is achieved and the percentage rents are collectible. Real estate tax and other cost reimbursements are recognized on an accrual basis over the periods in which the related expenditures are incurred. Other property income includes parking income, general excise tax billed to tenants and fees charged to tenants at our multifamily properties. Other property income is recognized when earned. We recognize general excise tax gross, with the amounts billed to tenants and customers recorded in other property income and