For 2014-2017 audit statistics, see the attached tables released by CRA under the Access to Information Act. The tables show tax earned by audit for various directorates & programs (GST, Criminal Investigations (CID), International Large Business (ILBD), Offshore Compliance (OCD), Small and Medium Enterprises (SMED) and SR&ED.
Based on the CRA AIA release, there were 20,456 SME audits in 2016-2017, with average “tax earned by audit” of $50,785. GST audits of SMEs generated about the same average TEBA, $51,470. For the same period, there were 62,028 GST Refund Integrity audits with average TEBA of $17,731.
Despite the relatively small number of audits, the CRA claims that by relying on risk assessment techniques, it detected non–compliance in 77% of the audits it carried out. (CRA Annual Report to Parliament 2014–2015, p. 61.)
Audit statistics are a guide to the likelihood a taxpayer will be reassessed but may not be a good guide to the ultimate tax liability from these reassessments. On the efficacy of objections in overturning assessments, see the 2016 Fall Report of the Auditor General of Canada, Report 2—Income Tax Objections—Canada Revenue Agency, which shows that up to 65% of objections are allowed in whole or part:
“2.67We found that in the past five fiscal years, 50 percent of the objections the Canada Revenue Agency received were allowed in full or in part. However, as mentioned in paragraph 2.65, not all objections received by the Agency were reviewed—some were dismissed. We found that the rate of objections allowed in full or in part increased to 65 percent when we examined only the files that the Agency actually reviewed and decided on.”
CRA AIA release of Audits by category – (TEBA $ & # of audits)