Definition
Adjusted Cost Base (ACB) is the running cost, in Canadian dollars, of a property you hold — the figure the Canada Revenue Agency (CRA) requires you to subtract from your proceeds when you calculate a capital gain or loss on disposition. For Bitcoin and other cryptocurrencies, ACB is the foundation of nearly every tax calculation a Canadian miner or holder makes. This is general information, not tax advice; confirm your own situation with a Canadian tax professional.
The average cost method
Because units of Bitcoin are identical property, the CRA does not let you pick which coins you sold. Instead you pool them and track a single average ACB per unit. If you buy 1 BTC at CAD $40,000 and later another at CAD $60,000, your pool is CAD $100,000 for 2 BTC, so your ACB is CAD $50,000 per coin. Every new acquisition re-averages the pool. Acquisition fees — exchange commissions, network fees paid to acquire the asset — are added to the ACB.
Why miners must track it carefully
When you receive mined coins, their fair market value at receipt becomes income, and that same value becomes the ACB of those coins going forward. When you later sell or swap them, you compare proceeds to that ACB to find your gain. Sloppy ACB records are the most common reason Canadian crypto filers get reassessed, because the CRA can challenge an unsupported cost figure. Keep dated records of every acquisition, fee, and disposition in CAD.
ACB feeds directly into your capital gains calculation, and a denied loss under the superficial loss rule is also added back to your ACB rather than lost outright.
In Simple Terms
Adjusted Cost Base (ACB) is the running cost, in Canadian dollars, of a property you hold — the figure the Canada Revenue Agency (CRA) requires…