A spreadsheet that breaks down who owns what in a startup. This may also include the calculations for ownership, dilution and liquidity for previous and future rounds. A well structured cap table is extremely important and should be reviewed by investors as part of a due diligence process:
Capital journey: is there adequate equity for future rounds of fundraising, do the founders and key stakeholders maintain meaningful ownership, or will some significant dilution be required?
Transparency - who are the current and previous investors, are there any with controlling positions (how are thier interests aligned?), are there any indications of disproportionate ownership positions or inconsistent valuations?
Is there an adequate employee option pool?
If the cap table is sub-optimal it can be a significant barrier to investment - it is better to fix this sooner rather than later.