ETF Adjustments

Why ETF holders get caught by ACB drift

ETF and mutual fund investors often have ACB changes that never show up in a broker’s simple book value display, because the broker only shows what you paid — not the distribution adjustments layered on top afterward. Return of capital (ROC) reduces ACB. Reinvested capital gain distributions increase it. DRIP purchases add both shares and cost to the pool. None of these are trades, so a ledger that only tracks buys and sells will silently drift away from the correct number.

The effect compounds over multi-year holds. For example, if an ETF distributes $0.50 per unit as return of capital across 200 units, your ACB decreases by $100 — from $5,000 to $4,900. That $100 is not taxed the year it is received; instead it is deferred into a larger capital gain (or smaller capital loss) whenever you eventually sell. Multiply that over five or ten years of annual ROC distributions and the gap between your broker’s displayed book value and your real ACB can become the largest source of error on your return. ROC amounts are reported to you on a T3 slip in Box 42, per CRA’s guidance on the tax treatment of mutual funds; the slip does not do the ACB math for you.

If those events are missed, the sale may later show too much gain or too little loss.

Supported adjustment types

myCostBase supports:

• DRIP transactions — a distribution is used to buy additional units automatically. This adds both units and cost to the pool, at the reinvestment price.
• Return of capital adjustments — reported in Box 42 of a T3 slip, ROC reduces your ACB per unit without changing your share count.
• Reinvested capital gain distributions — reported in Box 21 of a T3 slip, these increase your ACB because you are taxed on the distribution in the year it is paid, just as if you had received it in cash.
• Stock splits — the share count changes but the total ACB does not, so the ACB per unit is recalculated across the new share count.

Each one changes the running ACB or share count in a specific way, and the ledger shows the effect immediately after the row is applied — so you can see the ACB per unit before and after every event, not just the final total.

Worked example: purchase, return of capital, and DRIP

The table below follows a single ETF position through a purchase, a return of capital distribution, and a DRIP reinvestment, showing how each event moves the ACB.

Notice that the ROC distribution and the DRIP purchase happen to net out to the same dollar amount here — that is a coincidence of the example, not a rule. In practice the two events are independent: ROC is driven by the fund’s distribution policy, while DRIP reinvestment depends on the unit price on the reinvestment date. myCostBase records each event as its own row so you can see both effects separately, rather than a single netted adjustment that hides how the number was produced.

Why these events belong in the same ledger as buys and sells

The ACB problem gets harder when adjustments live in a separate notes file or spreadsheet tab, because every later sale then depends on someone remembering to check a second source before calculating the gain. myCostBase keeps ROC, DRIP, reinvested distributions, and splits inline in the same transaction ledger as buys and sells, in date order. That matters for two reasons: historical recalculation works correctly after you edit or backfill an earlier row, and the audit trail stays readable as one timeline instead of requiring you to cross-reference a trade list against a separate adjustments sheet when you (or CRA) need to explain how a number was reached.

What to keep on hand

For ETF adjustments, preserve the records that support each entry — T3 slips, the issuer’s year-end distribution breakdown, and any brokerage statement showing the reinvestment price and unit count for a DRIP. myCostBase can store the adjustment in the ledger, but the underlying source document is still what you would produce if CRA asked you to substantiate the number. As a general rule, CRA expects supporting records to be kept for six years from the end of the tax year they relate to, and indefinitely for anything supporting a carried-forward capital loss.

Where these adjustments show up later

Missed or mistimed ETF adjustments are one of the most common reasons broker-reported figures differ from myCostBase during reconciliation — a T5008 slip’s Box 20 cost figure typically reflects only what the broker tracked internally, not ROC or DRIP activity layered on afterward. If you want to see how those differences are surfaced for tax-year review, continue to T5008 Reconciliation and Reports.

Frequently asked questions

How does return of capital affect my ETF’s adjusted cost base?

Return of capital (ROC) distributions, reported in Box 42 of a T3 slip, reduce your ACB by the ROC amount per unit multiplied by the number of units you hold. This defers tax rather than eliminating it: the reduced ACB increases your capital gain (or reduces your capital loss) when you eventually sell.

Do reinvested distributions increase or decrease ACB?

It depends on the type. A reinvested capital gain distribution (Box 21 of a T3 slip) increases your ACB, because you are taxed on the distribution as if you received it in cash and then used it to buy more units. A DRIP purchase also increases your ACB by the reinvested amount and adds the new units to your share count. Return of capital is the exception that decreases ACB.

Can return of capital make my ACB go negative?

Yes, if cumulative ROC exceeds your original cost. When that happens, the CRA treats the excess as a capital gain in the year the ACB would otherwise go below zero, and your ACB resets to zero going forward.

Where do I find the return of capital amount for my ETF?

Your brokerage issues a T3 slip (or a summary of trust income allocations, for ETFs structured as mutual fund trusts) showing Box 42 for return of capital and Box 21 for capital gains distributions. Fund issuers also typically publish a year-end distribution breakdown for each ETF on their websites.