HMRC has updated P11D Working Sheet 2b (car and car fuel benefit provided via optional remuneration arrangements 2017 to 2018) and P11D working sheet 4 (interest free and low-interest loans 2017 to 2018).
These forms are final versions of P11D and P11D Working Sheets for tax year 2017 to 2018. They should only be used by software developers to help with development of their payroll software.