myCostBase helps Canadian investors maintain the adjusted cost base records needed for non-registered investment accounts. Instead of relying on a single broker's account-level book value, it pools identical securities across taxable accounts and brokerages for each taxpayer, creating a dated, reviewable ledger of every ACB change. Users can enter trades manually or import CSV history from supported Canadian brokerages. myCostBase handles purchases and sales, DRIPs, return of capital, reinvested distributions, transfers, stock splits, options, short sales, commissions, and USD transactions. Historical USD amounts are converted with Bank of Canada daily exchange rates, with the rate and calculation trail kept visible. At tax time, myCostBase compares its calculated proceeds, ACB, and realized gain or loss with broker T5008 figures and explains discrepancies such as return-of-capital adjustments or pooled holdings across institutions.