The document discusses potential areas where Canadian companies may have overpaid goods and services tax (GST) and be eligible for refunds. It notes that 9 out of 10 companies audited recovered significant overpayments going back 4 years. Some key areas where overpayments may have occurred include missed input tax credits, treatment of employee expenses, mail-in coupons, warranty expenses, foreign exchange issues, general ledger anomalies, and bad debts. The document emphasizes that competent tax reviews are important due to the complex nature of GST rules and the lack of time or expertise of most company tax departments to fully ensure compliance.