How to report a T5008: box 21 goes on Schedule 3, box 20 is not ACB

Where does each T5008 box go on the return?

Box 21 is the figure that lands on the return. The dealer reports the total proceeds there and isn't allowed to deduct expenses from them, while box 20 holds the dealer's cost or book value canada.ca. The gain is yours to compute: proceeds minus the adjusted cost base minus the outlays and expenses of the sale canada.ca.

Shares (SHS) and mutual fund trust units (MFT) usually go on line 4 of Part 3 of Schedule 3, with total proceeds on line 13199 and the gain or loss on line 13200, unless the shares are qualified small business corporation or farm or fishing shares with their own section. Bonds, debentures and similar debt (BON, DOB) go on line 6: proceeds on line 15199, gain or loss on line 15300 canada.ca. Those are the lines on the 2025 Schedule 3, the latest published as of October 2026. The full walkthrough is on the Schedule 3 page.

Capital gains shown on a T3 or T5013 are a different path: they go on line 17400 or 17600, not in Part 3 canada.ca.

Why box 20 can't stand in for your client's ACB

The CRA expects the dealer to take reasonable measures so box 20 is correct, and it also warns that the investor may have to adjust that amount to work out the ACB canada.ca. The dealer only sees its own account. Your client's ACB is an average across every identical share they own, recalculated at each purchase canada.ca, so shares of the same company held at a second broker change it. So do reinvested distributions, return of capital in T3 box 42 and a denied superficial loss. The method is on the adjusted cost base page.

Here is a client who holds XYZ shares at two brokers. The costs include purchase commissions. Broker A then sells its 300 shares for $9,000, with a $10 selling commission, and issues a T5008 showing $9,000 in box 21 and $6,300 in box 20.

The cost of the shares sold is 300 × $24.60 = $7,380, so the gain is $9,000 − $7,380 − $10 = $1,610. Using box 20 would overstate the taxable gain by $540. The error also runs the other way later: Broker B still shows $6,000 of book value for 200 shares whose ACB is now $4,920, so its eventual T5008 will understate that gain by $1,080. At the 50% inclusion rate (see capital gains inclusion rate 2026), every dollar of ACB error moves taxable income by 50 cents.

What do you do when box 20 is blank or wrong?

Rebuild the cost from your client's own records: trade confirmations, monthly statements, DRIP records and T3 slips. The CRA describes book value as the total paid for a security, including transaction charges on the purchase, adjusted for reinvested distributions, returns of capital and corporate reorganizations canada.ca. That's the same building block as ACB, but only for what the dealer can see.

Never leave the ACB at zero to get the return filed. With no cost, the whole of box 21 becomes the gain. If the records are gone, document how you reconstructed the cost (old statements, the transferring broker, historical prices on the purchase dates) and keep that file with the return.

Book value goes the other way too. The CRA tells dealers not to put the market value or the sale price in box 20 canada.ca. If box 20 equals box 21 to the cent, treat it as a placeholder and rebuild the cost.

Which T5008 sales don't go on Schedule 3?

Sales inside registered plans. Dealers don't have to report sales made for a person exempt from tax under section 149, and the guide names RRSPs as an example canada.ca. Income earned in an RRSP is usually exempt while it stays in the plan canada.ca, and interest, dividends and capital gains earned in a TFSA are generally tax free canada.ca. If a slip shows up for a registered account, leave it off Schedule 3.

Some dispositions never get a slip but still go on the return. Dealers don't report deemed dispositions or the expiry or exercise of an option, right or warrant on a T5008 canada.ca. A deemed disposition still belongs on your client's return, so the missing slip is no reason to skip it (see deemed disposition on death). Units of a trust that trade at a constant fixed price in Canadian dollars, such as money market funds, are excluded from T5008 reporting canada.ca.

Treasury bills split in two. When a bill is sold before maturity, the interest accrued to the sale date is interest income, and only the rest is a capital gain or loss. The CRA's example: a bill bought for $49,500 and sold 44 days later for $49,750 at a 4.05% yield has $241.67 of interest ($49,500 × 4.05% × 44 ÷ 365), so net proceeds are $49,508.33 and the capital gain is $8.33 canada.ca. For a linked note, the box 21 proceeds exclude the interest already reported in T5 box 30 canada.ca.

The slip does not decide capital versus income

A T5008 reports a sale, not its character. The CRA says you need to decide whether a transaction is capital or income, and that the facts surrounding it determine the nature of the gain or loss canada.ca. When a client trades often enough that the gains may be business income, the tests are on the day trading tax page.

For Canadian securities, your client can remove the doubt with the section 39(4) election, which deems every Canadian security they own to be capital property laws-lois.justice.gc.ca. It's made on Form T123 attached to the return, and once made it can't be reversed canada.ca. Section 39(5) shuts out a trader or dealer in securities, a financial institution, a corporation whose principal business is lending money or buying debt, and a non resident laws-lois.justice.gc.ca.

A US dollar T5008 needs two exchange rates

Box 13 shows the currency code when the amounts aren't in Canadian dollars canada.ca. Convert the proceeds at the exchange rate when the sale happened, the ACB at the rate when the shares were bought, and outlays at the rate when they were incurred canada.ca. Which rate to use is on foreign income exchange rate.

Converting box 20 at the sale date rate is the common mistake. Say your client bought 100 shares for US$5,000 when US$1 cost C$1.30 and sold them for US$6,000 when it cost C$1.40. The ACB is C$6,500 and the proceeds are C$8,400, for a C$1,900 gain. Converting the US$1,000 gain at 1.40 gives C$1,400, which misses the currency gain on the cost.