Cost
prop("Paid") / (1 + if(empty(prop("VAT Rate")), 23, toNumber(prop("VAT Rate"))) / 100)
VAT
prop("Paid") / (1 + if(empty(prop("VAT Rate")), 23, toNumber(prop("VAT Rate"))) / 100) * if(empty(prop("VAT Rate")), 23, toNumber(prop("VAT Rate"))) / 100