Start with the taxpayer
One taxpayer equals one pooled adjusted cost base universe. That is the rule that drives the rest of the setup. If the same taxpayer holds an identical security across two taxable brokerages, those positions belong to the same ACB pool even if the broker statements never meet.
Create the taxpayer first, then add the brokers that belong to that person.
Mark taxable versus excluded accounts correctly
This is the most important setup decision in the product.
Taxable accounts belong in the pool. Registered accounts do not. In practice, that means non-registered cash or margin accounts should be marked taxable, while RRSP, TFSA, FHSA, and RESP accounts should be excluded.
If you classify these incorrectly, the final ACB result can be wrong even if every transaction row was imported perfectly.
Add accounts before importing history
For each account, record:
- institution name;
- account nickname;
- whether the account is taxable or excluded.
The nickname matters because later ledger rows and warnings need to show which brokerage account produced the event.
Decide how you will load history
There are two valid starting paths:
- import a broker CSV;
- enter transactions manually.
The free plan is designed to support manual entry first, so you can validate the ledger without paying for imports. If your history is long, imports will save time, but you still need the setup decisions above to be correct before the import starts.
Gather the records that commonly go missing
Before you start, collect anything that broker exports usually fail to carry cleanly:
- transfer documentation showing original cost basis;
- ETF tax adjustments such as return of capital and reinvested capital gains;
- notes on FX overrides if you already rely on documented custom rates.
These are the cases that usually break spreadsheet-based ACB tracking later.
Common setup mistakes
- Marking a joint account as one taxpayer. A joint non-registered account is typically split between spouses for tax purposes — each spouse’s share belongs to their own ACB pool, not a single shared one.
- Starting the ledger from the current year instead of the first purchase. If you’ve held a security for years, a partial history understates the pooled ACB — see “Backfilling history” below.
- Skipping account classification because it seems obvious. Margin, cash, and non-registered accounts still need to be explicitly marked taxable — an unclassified account is excluded from calculations by default until you confirm it.
Backfilling history
If you already held a security before you started using myCostBase, the pooled ACB is only complete once history reaches back to the first purchase of that identical property, not just the current tax year. Import or manually reconstruct from that first purchase forward, even if it means adding a few older transactions by hand before your CSV history picks up.
What to do next
If you are ready to load source history, continue to Importing Transactions. If your main concern is understanding how multiple brokerages roll into one ACB number, read Pooled ACB Across Brokerages.