How do I calculate the adjusted cost base for T5008?

[t756dcy]

The information attached says it may or may not reflect the adjusted cost base in box 20. How do I know if it is already adjusted?

[TurboTaxSusan]

Box 20 of the T5008 is cost or book value, which is the total amount paid to purchase a security, including any transaction charges related to the purchase, adjusted for reinvested distributions, returns of capital and corporate reorganizations. 

The adjusted cost base (ACB) is usually the cost of a property plus any expenses to acquire it, such as commissions and legal fees. You would use the amount in Box 20 to help you to calculate the adjusted cost base, though in some cases what is in Box 20 may equal your ACB.