The notional interest deduction rate for an assessment year (e.g. 2019) is calculated on the basis of the average return of the 10-year OLO in the months of July, August and September of the penultimate year preceding the assessment year (e.g. 2017).
This rate is still subject to official confirmation. As a reminder, the rate for assessment year 2018 is 0,237% (0,737% for SMEs).
Last July, the federal government has reached an agreement on the corporate tax reform that will modify the equity base which is used to calculate the notional interest deduction (incremental equity instead of total equity) (see our e-tax flash). More details will follow when the draft legislation becomes available.