Cost Basis And Why The Records Matter

Cost basis is the figure representing what was paid for an investment, adjusted for various events. It exists for reporting purposes and becomes relevant only when something is sold.

What the figure includes

Basis starts with the purchase price and is adjusted by commissions and by subsequent events affecting the position. It is a running figure rather than a fixed one, revised each time something happens to the holding.

Reinvested distributions add to basis, because each reinvestment is a purchase of additional shares even though no new money arrived.

Corporate actions such as splits, spinoffs and returns of capital all adjust the figure, and the rules for each are specific rather than intuitive.

Who is responsible for tracking it

Brokers are required to report basis to the account holder and to the authorities for securities acquired after specified dates, which differ by security type.

Positions acquired before those dates, or transferred in without complete records, may appear with missing or unverified basis on statements.

The account holder remains responsible for the accuracy of what is ultimately reported, regardless of what a statement displays.

Lot selection and default methods

When only part of a position is sold, which shares are treated as sold depends on the identification method in effect at the time of the trade.

Firms apply a default method unless instructed otherwise, and mutual funds commonly use an averaging method that operates differently from individual share identification.

Changing the method or identifying specific lots generally must be done at or before the sale, since retroactive changes are constrained.

Where records commonly break down

Transfers between firms, inherited holdings, positions from an employer plan and long-held certificates are the recurring sources of missing basis.

Reconstructing a history years later means locating old confirmations and reconstructing corporate actions, which is time-consuming and sometimes impossible.

Keeping annual statements and trade confirmations in one place is a low-effort habit that eliminates most of this difficulty. Firms are not obliged to retain records indefinitely, and a provider that has been acquired may hold nothing from before the transition.

Why this is professional territory

The consequences of a sale depend on holding periods, account types, offsetting transactions and individual circumstances, and the applicable rules change over time.

Inherited positions and holdings passing through an estate follow separate rules that vary by situation and by state.

The general point is that records determine outcomes, and the specific treatment of any transaction is a question for a qualified tax professional.