Why client ACB is your hardest Schedule 3 problem
Capital gains look simple: proceeds minus cost. But the cost is where engagements blow up. The CRA expects a pooled adjusted cost base that accounts for every purchase, DRIP reinvestment, return of capital, corporate action, and FX conversion — across every non-registered account the client has ever held the security in.
Most clients hand you a stack of T5008 slips and expect you to file. The slip’s cost box is blank, wrong, or incomplete roughly half the time. If you copy it, you’re either leaving money on the table for the client (overstated gain) or exposing both of you to a reassessment (understated gain).
The client intake questionnaire
Before you touch the numbers, ask these questions:
- How many brokerages? — Every institution where they hold or have held non-registered investments. Pooling rule demands all of them.
- Any transfers between brokers? — In-kind transfers don’t change ACB but often leave the receiving broker with a blank or wrong cost. Get the original purchase records.
- DRIP? — Reinvested dividends are purchases that raise ACB. Many clients forget these entirely.
- Return of capital? — ETFs and REITs frequently distribute ROC (T3 box 42) that reduces ACB each year. Has the client tracked these?
- Corporate actions? — Stock splits, spin-offs, mergers, and name changes all reallocate ACB.
- Equity compensation? — RSUs and ESPPs have a cost base equal to the employment income inclusion amount at vest/purchase, not zero.
- USD trades? — Every US-dollar purchase and sale needs BoC-rate conversion to CAD on the applicable transaction date.
- Inherited or gifted shares? — Different rules for ACB on death (FMV at death), gifts (usually donor’s ACB), and spousal transfers.
What data to request
For a defensible ACB rebuild, you need:
| Source | What it gives you | Limitation |
|---|---|---|
| Transaction history export (CSV/PDF) | Every buy, sell, dividend, and distribution with dates and amounts | Only for the current broker and account; doesn’t cover prior brokers |
| T5008 slips (current year) | Proceeds (reliable) and cost (unreliable) for dispositions | Cost is often blank, account-limited, or broker book value |
| T3 slips (all years held) | Box 42 return of capital; box 21 capital gains allocations | Clients rarely keep prior-year T3s — may need to pull from CRA My Account or AFR |
| Transfer confirmations | Proof of in-kind transfer date and quantity (no deemed disposition) | Doesn’t tell you the original cost — you need the sending broker’s records |
| Corporate action notices | Spin-off allocation ratios, merger terms, split details | Clients frequently discard these; check the issuer’s investor relations page |
| Prior-year returns | Previously reported gains/losses that reduce the pool; prior reserves | Doesn’t directly give you remaining ACB unless the working paper survived |
Rebuilding ACB from incomplete records
In practice, records are never complete. The professional approach is to build the best defensible estimate from what’s available:
Tier 1: Full history available
If the client has a complete transaction history from day one (or you can export it from the broker), rebuild the ACB chronologically: every buy adds to the pool, every sale removes at the weighted average, every ROC reduces the pool, every DRIP increases it. This is the gold standard.
Tier 2: Partial history
If records are incomplete (e.g., the client transferred from an old broker years ago and lost those records), use the earliest available cost basis and document the gap. Options:
- Use the sending broker’s transfer statement (if available) as a starting point
- Use the market value on the date they opened the current account (conservative approach — may overstate ACB slightly)
- Request historical data from CRA My Account (T5008s go back several years)
- Use historical price data for the known purchase dates
Tier 3: Minimal records
If the client has virtually no records and the holdings are old, the fallback is:
- Historical price lookup for the approximate purchase period
- $0 ACB (most conservative — overstates the gain but is defensible as a worst case)
- Document that you used the best available information and the methodology
The six errors you’re probably seeing
- $0 ACB from RSUs: The client’s employer reported an employment benefit (T4 box 38), but the broker shows $0 cost. The ACB is the vest-date FMV per share × shares. This is the most expensive error in tech-sector returns.
- Ignoring ROC for years: A client held an ETF for 7 years and never reduced their ACB for T3 box 42. Their true ACB may be thousands lower than they think (larger gain at sale).
- Per-broker cost instead of pooled: Client holds RY at two brokers, sells at one. That broker’s cost reflects only its shares — the true ACB pools both. Could go either direction.
- Missing DRIPs: Reinvested dividends over a decade can add 10-20% to the ACB. Missing them means overstating the gain at sale.
- FX on US stocks: Using the USD purchase price without CAD conversion at the buy date. Every trade needs a separate BoC rate lookup.
- Transferred-in shares at market value: The receiving broker recorded market value on the transfer date. The true ACB is the original pooled cost — which could be much higher or lower.
Documentation and working paper standards
Your ACB working paper should support the filed figure if the CRA reviews. Include:
- Security identification: Name, ticker, CUSIP/ISIN
- Position history: Chronological buys/sells/adjustments with dates, quantities, and per-unit amounts
- Running ACB: The pooled cost after each transaction
- Adjustment sources: Which T3 slip provided the ROC figure, which corporate action notice provided the allocation ratio
- Data gaps: Explicit documentation of what records were unavailable and what methodology you used to fill them
- Methodology note: "ACB reconstructed from [source] using [method] — see attached transaction history and T3 slips"
This working paper replaces the unreliable T5008 as your Schedule 3 source. If the CRA queries, you produce this — not the slip.
The filing workflow
Efficient capital gains filing for accountants:
- Pull AFR — get the T5008 dispositions the CRA expects to see. Use proceeds for reconciliation.
- Rebuild ACB — from client data, transaction history, T3 slips, and any required estimation methodology.
- Reconcile — match each T5008 to your ACB records. Override box 20 with the correct pooled ACB. Flag missing slips or extra dispositions.
- Prepare Schedule 3 — group dispositions by security (same pool = one line), with correct proceeds, ACB, and outlays.
- Import into tax software — TaxCycle field-code import, ProFile workpaper, or DT Max rapid entry.
- Verify control totals — software total proceeds, ACB, and gain match your working paper.
- File and retain — keep the ACB working paper as engagement documentation.
When to push back on the engagement
Some clients present a volume/complexity level that makes manual ACB reconstruction uneconomical:
- 100+ dispositions per year across multiple brokers with DRIPs, ROC, and corporate actions
- Active options traders where premium tracking, assignment, and exercise create dozens of ACB adjustments
- Multi-year gap in records with no recoverable data
- Crypto portfolios with hundreds of wallet-to-wallet transfers and DeFi interactions
In these cases, the engagement needs either (a) a capital gains tracking tool that the client uses prospectively, or (b) a specialist reconstruction engagement priced separately from the personal return.