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, 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 we satisfy performance obligations as evidenced by the transfer of control of our services to customers. We measure other property income based on the amount of consideration we expect to be entitled to in exchange for the services provided. We recognize general excise tax gross, with the amounts billed to tenants and customers recorded in other property income and the related taxes paid as rental expense. The general excise tax included in other income was $3.5 million, $3.6 million and $3.7 million for the years ended December 31, 2019, 2018 and 2017, respectively. For a tenant to terminate its lease agreement prior to the end of the agreed term, we may require that they pay a fee to cancel the lease agreement. Lease termination fees for which the tenant has relinquished control of the space are generally recognized on the later of the termination date or the satisfaction of all conditions precedent to the lease termination, including, without limitation, payment of all lease termination fees. When a lease is terminated early but the tenant continues to control the space under a modified lease agreement, the lease termination fee is generally recognized evenly over the remaining term of the modified lease agreement.
Current accounts receivable from tenants primarily relate to contractual minimum rent and percentage rent as well as real estate tax and other cost reimbursements. Accounts receivable from straight-line rent is typically longer term in nature and relates to the cumulative amount by which straight-line rental income recorded to date exceeds cash rents billed to date under the contractual lease agreement.
We recognize revenue on the hotel portion of our mixed-use property from the rental of hotel rooms and guest services when we satisfy performance obligations as evidenced by the transfer of control when the rooms are occupied and services have been provided. Food and beverage sales are recognized when the customer has been served or at the time the transaction occurs. Revenue from room rental is included in rental revenue on the statement of income. Revenue from other sales and services provided is included in other property income on the statement of income.
We make estimates of the collectability of our current accounts receivable and straight-line rents receivable which requires significant judgment by management. The collectability of receivables is affected by numerous different factors including current economic conditions, tenant bankruptcies, the status of collectability of current cash rents receivable, tenants' recent and historical financial and operating results, changes in our tenants' credit ratings, communications between our operating personnel and tenants, the extent of security deposits and letters of credits held with respect to tenants, and the ability of the tenant to perform under the terms of their lease agreement. If our assessment of these factors indicates it is probable that we will be unable to collect substantially all rents, we recognize a charge to rental income and limit our rental income to the lesser of lease income on a straight-line basis plus variable rents when they become accruable or cash collected. If we change our conclusion regarding the probability of collecting rent payments required by a lessee, we may recognize an adjustment to rental income in the period we make a change to our prior conclusion.
At December 31, 2019 and December 31, 2018, our allowance for doubtful accounts was $1.2 million and $0.6 million, respectively. Our allowance for deferred rent receivables at December 31, 2019 and December 31, 2018 was $0.5 million and $0.3 million, respectively. Total bad debt expense was $1.8 million, $0.8 million and $0.8 million for the years ended December 31, 2019, 2018 and 2017, respectively. Total bad debt expense for the year ended December 31, 2019 was included as a reduction to rental income on the statement of income while the total bad debt expense for the years ended December 31, 2018 and 2017 were included in rental income on the statement of income.
Effective January 1, 2018, (upon the adoption of ASU 2014-09, Revenue from Contracts with Customers) sales of real estate are recognized generally upon the transfer of control, which usually occurs when the real estate is legally sold. Prior to January 1, 2018, sales of real estate were recognized only when sufficient down payments had been obtained, possession and other attributes of ownership had been transferred to the buyer and we had no significant continuing involvement. The application of these criteria can be complex and required us to make assumptions. We believe the relevant criteria were met for all real estate sold during the periods presented.