---
title: Cost basis vs market value: why both matter
url: https://wealthscout.app/updates/portfolio-value-vs-cost-base
category: Shares & ETFs
updated: 2026-08-23
---

# Cost basis vs market value: why both matter

Source: https://wealthscout.app/updates/portfolio-value-vs-cost-base

Use current market value for today's balance sheet and net worth tracking. Use cost basis purely as the acquisition and adjustment history required by tax authorities. Their difference is your unrealized gain or loss, but remember: cost basis is not a measure of your overall investment performance.

## Takeaways

- Market value is the current estimated sale value of your holdings.
- Cost basis is a historical record of purchase costs and adjustments, used for tax purposes.
- Cost basis does not equal performance. Both numbers are useful, but they answer different questions.

**Scope.** Cost basis rules can change depending on your brokerage, corporate actions, non-assessable payments, dividend reinvestments, and local tax jurisdiction. This guide does not calculate personal tax.

## Maintain both scorecards


## Questions

## Sources

- [Sale of shares or units](https://www.ato.gov.au/forms-and-instructions/capital-gains-tax-personal-investors-guide-2021/part-b-sale-of-shares-or-units) — Australian Taxation Office
- [Keeping records for capital gains tax](https://www.ato.gov.au/forms-and-instructions/capital-gains-tax-guide-2022/part-a-about-capital-gains-tax/keeping-records) — Australian Taxation Office