A notional or arbitrary assessment is an assessment the Canada Revenue Agency raises when a taxpayer has not filed a required return. Using the information available to it — often prior-year figures for a business — the CRA estimates income and issues an assessment, typically without the benefit of any deductions, so the figure is frequently higher than the taxpayer's actual liability.
The assessment is legally valid and enforceable until displaced. The intended effect is to prompt the taxpayer to file an accurate return, which the CRA then processes and reassesses to the correct amounts. Where the deadline to object to the notional assessment has passed, an extension application or other relief may be needed to dispute the resulting balance.