My T5008 cost is missing or looks wrong. Will I pay too much tax?

Arsen Accounting Services · T1 guide · Sources checked October 29, 2026

A blank or incorrect cost figure can produce the wrong gain if it is imported without review. The sale proceeds on a T5008 are not automatically your profit. Compare the slip with your purchase history and adjusted cost base before filing. CRA: T5008 box 20 and transaction reporting CRA: Calculating gains and currency conversions

What box 20 does—and does not—tell you

Box 20 is the cost or book value. CRA cautions that it may not equal your adjusted cost base, often shortened to ACB. Transfers between brokers, reinvested distributions and other adjustments can leave information that needs checking. A missing box does not prove the investment cost nothing. CRA: T5008 box 20 and transaction reporting

Ask the institution for its transaction history and any available cost explanation. Keep earlier broker statements if the holding moved between accounts. When records disagree, preserve both versions instead of replacing the figure with an estimate that cannot be explained.

Work out the gain from the underlying records

For capital-property sales, the basic calculation is proceeds minus adjusted cost base and selling expenses. Purchase commissions generally form part of cost; selling costs are considered separately. The classification of an activity as investing or a business must also be correct. CRA: Calculating gains and currency conversions CRA: Capital gains guide

Holdings acquired at different times, reinvested amounts and returns of capital may need a running cost record. A year-end market value is not a substitute for that history. Tell your preparer about stock splits, reorganizations, inherited holdings and transfers rather than assuming each slip contains the whole calculation. CRA: Capital gains guide

Check US-dollar transactions carefully

CRA requires the relevant amounts in Canadian dollars. Proceeds use the exchange rate at the sale date, cost uses the rate when the property was acquired, and expenses use the rate when incurred. Applying one sale-date rate to the entire gain can give a different answer. CRA: Calculating gains and currency conversions

Look at the currency code on the slip and the currency used in the tax software. An imported number deserves the same review as a number typed manually. Keep the exchange-rate method and transaction dates with the calculation.

Reconcile each sale once

Create a list of sales and mark which document supports each one: T5008, broker gain/loss report or your own calculation. These may describe the same transaction. Reconcile them so a sale is not accidentally entered twice or omitted while correcting an import.

• Collect purchase and sale confirmations, including fees and currencies.
• Obtain historical statements from former brokers.
• Bring T3 slips and distribution records relevant to cost adjustments.
• Identify transfers, corporate actions and holdings in several accounts.
• Explain any difference between your calculation and the broker’s report.

Common questions

Does CRA already having the slip mean the gain is correct?

No. CRA’s T5008 instructions expressly recognize that box 20 may need adjustment to arrive at the investor’s ACB. CRA: T5008 box 20 and transaction reporting

What if an earlier return used the wrong figure?

Reconstruct the correct calculation and discuss an adjustment for that year. Keep the original documents and a clear explanation of what changed.

Bring the history, not only the slip

Arsen Accounting provides investment tax reporting. Mention the number of accounts, approximate trading volume, currencies and missing records so the scope can be assessed. Our document checklist is a useful starting point.

Discuss your tax preparation