Cost basis
What an asset cost to acquire, used as the starting point for computing a gain or a loss on disposal.
Updated 2026-07-26
In its simplest form the basis is what was paid, including the fees that were part of acquiring it. It matters because a disposal is measured against it, and because tax rules in most jurisdictions are written in terms of it.
The complications are all in the details, and the details are jurisdiction-specific: which fees may be added, how corporate actions adjust the figure, which lot is treated as sold when several were bought at different prices, and how transfers between accounts carry basis with them.
The calculator on this site does arithmetic on lots you enter and shows the working. It does not know your jurisdiction, it does not know your account history, and it is not a tax computation.
Related terms
3 entries- FIFO
- Matching a disposal against the earliest acquired lots first, oldest before newest.
- Form 4
- The filing in which a company insider reports a change in their holdings, normally within two business days.
- Open market purchase
- An insider buying shares on the market with their own money, reported under transaction code P.