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One approach to risk-limiting audits (RLAs) compares ran- domly selected cast vote records (CVRs) to votes read by human auditors from the corresponding ballot cards. Historically, such methods reduce audit sample sizes by considering how each sampled CVR di!ers from the corresponding true vote, not merely whether they di!er. Here we investigate the latter approach, auditing by testing whether the total number of mismatches in the full set of CVRs exceeds the minimum number of CVR errors required for the reported outcome to be wrong (the “CVR margin”). This strategy makes it possible to audit more social choice functions and simplifies RLAs conceptually, which makes it easier to explain than some other RLA approaches. The cost is larger sample sizes. “Mismatch-based RLAs” only require a lower bound on the CVR margin, which for some social choice functions is easier to calculate than the e!ect of particular errors. When the population rate of mismatches is low and the lower bound on the CVR margin is close to the true CVR margin, the increase in sample size is small. However, the increase may be very large when errors include errors that, if corrected, would widen the CVR margin rather than narrow it; errors a!ect the margin between candidates other than the reported winner with the fewest votes and the reported loser with the most votes; or errors that a!ect di!erent margins.