Notice 2018-99 explains that the number of reserved nonemployee spaces in the

parking facility, or portion thereof, may be exclusively reserved for nonemployees by a variety of methods, including, but not limited to, specific signage (for example, “Customer Parking Only”) or a separate facility or portion of a facility segregated by a barrier to entry or limited by terms of access. A taxpayer that has no reserved nonemployee spaces may proceed to Step 4.

A taxpayer that has reserved nonemployee spaces may determine the percentage of reserved nonemployee spaces in relation to the remaining total parking spaces and multiply that percentage by the taxpayer’s remaining total parking expenses. The product is the amount of the deduction for remaining total parking expenses that is not disallowed under section 274(a)(4).

iv. Step 4

Fourth, the taxpayer determines the remaining use and allocable expenses of any remaining parking spaces. If the taxpayer completes Steps 1 through 3 of the method in Notice 2018-99 and has any remaining parking expenses not specifically categorized as deductible or nondeductible, the taxpayer must reasonably determine the employee use of the remaining parking spaces during normal business hours

on a typical business day and the related expenses allocable to employee parking spaces. Methods to determine employee use of the remaining parking spaces may include specifically identifying the number of employee spaces based on actual or estimated usage. Actual or estimated usage may be based on the number of spaces, the number of employees, the hours of use, or other measures.

C. Comments on Notice 2018-99