If you receive a T5008 for a securities transaction, Box 20 and Box 21 answer different questions. Box 20 reports cost or book value. Box 21 reports proceeds of disposition or settlement amount.
Neither field should be copied into Schedule 3 without checking the underlying transaction and records. Box 20 may or may not reflect your adjusted cost base, and Box 21 should be checked for currency and commission treatment.
Written and researched by myCostBase. Last reviewed: September 2, 2026. This article was checked against current CRA and brokerage documentation linked below. The explanation is usable without the product.
Quick comparison
| T5008 field | What it reports | How to use it |
|---|---|---|
| Box 20 | Cost or book value | Compare with your independently supported ACB. It may agree, differ or be blank. |
| Box 21 | Proceeds of disposition or settlement amount | Compare with the trade confirmation and verify whether selling expenses have already been netted. |
For a complete reconciliation example, including pooled ACB and the final Schedule 3 entries, see T5008 Box 20 and Adjusted Cost Base.
Box 20: cost or book value
CRA’s T5008 guide describes Box 20 as the cost or book value of the securities involved.
The guide tells preparers to take reasonable measures to:
- include purchase transaction charges in the cost;
- adjust for reinvested distributions;
- adjust for return of capital;
- reflect reorganizations and other relevant changes.
That makes Box 20 more than an arbitrary internal number. It can be a valuable cross-check. CRA nevertheless cautions individual investors that Box 20 may or may not reflect their adjusted cost base and that they must make the adjustments needed for tax reporting.
A difference can arise because the broker does not know about identical securities held at another institution, complete transfer history was not transmitted, an outside DRIP is missing, or an annual fund adjustment has not yet been posted.
For the broader broker-data question, see Broker Book Value vs Adjusted Cost Base.
Box 21: proceeds of disposition
Box 21 is the proceeds of disposition or settlement amount. CRA instructs T5008 preparers to report total proceeds and not deduct expenses incurred to dispose of the securities.
The trade confirmation should still be checked. Interactive Brokers Canada’s published T5008 guidance, for example, describes its Box 21 as gross proceeds less commissions and fees. That differs from CRA’s preparer instruction and shows why investors should verify the actual slip rather than assume every broker follows the same presentation.
Before completing Schedule 3, confirm:
- the security and quantity;
- the settlement date;
- the currency code and Canadian-dollar amount;
- whether a selling commission or fee is already included in the reported amount.
If a commission has already reduced Box 21, do not enter it again as a separate outlay or expense.
Why Box 20 may not equal adjusted cost base
Adjusted cost base can depend on information outside one brokerage account:
- identical properties held by the same taxpayer at another taxable brokerage;
- purchases, sales or DRIPs that occurred before a transfer;
- return-of-capital and reinvested-distribution adjustments;
- corporate actions;
- foreign-currency conversion at the relevant transaction dates;
- other taxpayer-specific adjustments.
The direction of the difference depends on the missing facts. Box 20 can be higher or lower than ACB. In a simple, complete single-broker history, the two figures may agree.
For the detailed cause-and-effect analysis, use T5008 Box 20 and Adjusted Cost Base rather than trying to diagnose the difference from this field-definition page alone.
From the T5008 to Schedule 3
Schedule 3 separates the three components of the capital-gain calculation:
| Schedule 3 component | Starting evidence | What to verify |
|---|---|---|
| Proceeds of disposition | T5008 Box 21 and sale confirmation | Gross or net presentation, currency and quantity |
| Adjusted cost base | Complete ACB ledger, with Box 20 as a cross-check | Identical-property pooling, transfers and adjustments |
| Outlays and expenses | Trade confirmation | Selling commission or fees not already netted from proceeds |
The calculation is:
Capital gain or loss = proceeds − adjusted cost base − outlays and expenses
Keeping the fields separate makes the calculation easier to review and prevents the same commission from being deducted twice.
When Box 20 is a useful cross-check
Box 20 can help:
- identify that the broker has no cost on file;
- reveal a missing transaction, transfer or annual adjustment;
- corroborate an independently maintained ledger;
- confirm a simple position held entirely at one institution;
- focus attention on material differences before filing.
Agreement is useful evidence, not proof that information outside the broker’s records was included.
The T5008 ACB reconciliation checker can compare Box 20 with your supported ACB. The Canadian Adjusted Cost Base Checklist provides the complete document-collection and accountant-handoff workflow.
What if Box 20 is blank or zero?
A blank or zero Box 20 does not mean ACB is zero. It means no usable cost was reported in that field.
Reconstruct the cost using available evidence such as:
- original trade confirmations;
- prior brokerage statements;
- transfer documents;
- DRIP and distribution records;
- corporate-action notices;
- earlier ACB ledgers or tax-preparer working papers.
If the historical amount is material and cannot be supported, obtain professional advice rather than substituting zero or the current market value.
Sources and calculation notes
- CRA: T5008 Guide—Return of Securities Transactions
- CRA: T5008 slip information for individuals
- CRA: Completing Schedule 3
- CRA: Capital Gains—T4037
- Interactive Brokers Canada: Tax information and reporting
Calculations and field descriptions should be checked against the tax-year slip and current source documentation. Corrections can be reported through the myCostBase contact page.
The application can compare a recorded ACB with T5008 values, but the result still depends on complete transactions and supporting adjustments. Use the free T5008 reconciliation checker →
Frequently asked questions
What does T5008 Box 20 contain?
Box 20 contains cost or book value. CRA tells T5008 preparers to take reasonable measures to include purchase transaction charges and adjustments for reinvested distributions, return of capital and reorganizations. CRA also cautions that Box 20 may or may not reflect the investor’s adjusted cost base.
What does T5008 Box 21 contain?
Box 21 contains proceeds of disposition or settlement amount. CRA instructs preparers to report total proceeds without deducting disposition expenses, but investors should verify the amount against the trade confirmation and avoid deducting a commission twice if a broker has already netted it.
Which T5008 numbers do I use on Schedule 3?
Use the supported proceeds, adjusted cost base and outlays or expenses for the disposition. Box 21 is a starting point for proceeds and Box 20 is a cross-check for ACB. Verify both against your own records before completing Schedule 3.
What if T5008 Box 20 is blank or zero?
A blank or zero Box 20 does not prove that adjusted cost base is zero. Reconstruct the cost from trade confirmations, transfer records, statements and other supporting documents, then use the supported ACB on Schedule 3.
General information only — not tax, legal, or financial advice. Consult a qualified professional for advice specific to your situation.