# Trading journal > A trading journal is a record of each trade — its entry, exit, size, reason and result — kept so that the trader's own behaviour can be reviewed. - Canonical: https://hadalinstruments.com/glossary/trading-journal/ - Term set: https://hadalinstruments.com/glossary/ --- A trading journal is the trader's own account of the trades taken, kept beside the broker's. Its most useful field is the reason for each entry, written before the result is known, together with the plan the trade was meant to follow. Entry, exit, size and result complete the row, and the rows are what a later review reads. The journal's limit is the limit of any single record. [What can a trading statement prove?](/research/what-can-a-trading-statement-prove/) sets it out for the broker's file: a record generated from one source agrees with itself by construction, so its consistency proves its arithmetic and little else. A journal fed from the same fills inherits that boundary. It can show the gap between the price asked for and the price filled, but the market at that instant needs a second record, and the belief that a statement proves the broker slipped the fill sits on the [refutation index](/refutations/#claim-3f96e3fc) as misleading. A journal's strength is behaviour. Read against its own stated reasons, a journal shows whether trades followed the plan, which setups were taken and which were skipped, and how size changed from one trade to the next. Those are questions about the trader rather than the market, and the journal is the record that can answer them. The measurement it supports is twofold: what a journal's records can prove, and how many trades an edge needs before it stops being consistent with luck. The [sample-size check](/tools/sample-size-check/) takes the log and returns that luck horizon, and it refuses below its floor rather than report a verdict the sample cannot carry. The same discipline, applied to software, is the append-only registry and crash-honest journaling bus behind [Fail-Visible Ops](/instruments/fail-visible-ops/), where silence counts as a fault rather than a status. What a trading journal cannot carry is a verdict on its own. It records decisions and results; whether the results show an edge is a sample-size question, and whether the fills were fair is a question for a second record. This entry recommends no template and names no number of trades that suffices. ## Commonly confused with Neighbouring concepts that get used interchangeably, and the distinction that actually separates them. - **Trading statement** — A statement is the broker's record, generated from one ledger, so its parts agree with each other by construction. A journal is the trader's own record of the same trades, and its value is what the statement has no field for: the reason each trade was taken and the plan it was meant to follow. - **[Kill ledger](https://hadalinstruments.com/glossary/kill-ledger/)** — A kill ledger records every strategy configuration that was tried and abandoned, so the true number of trials is known. A journal records the trades one strategy took. One counts ideas; the other reviews a single idea's behaviour in the market. - **[Backtesting](https://hadalinstruments.com/glossary/backtesting/)** — A backtest replays a rule over past data under the assumptions it declares. A journal records what happened when real orders met a real market, fills and costs included, so the two disagree exactly where the backtest's assumptions did. ## How to measure it in your own data A definition you cannot test is a definition you have to take on trust. This is the shortest honest route from the concept to a number you computed yourself. - **Records you need** — Every closed trade with its entry, exit, size, reason and result, and the same trades as the broker's statement reports them. - **What you compute** — Reconcile the journal's fills with the statement first. Then give the per-trade results to the sample-size check, which returns the luck horizon: how many trades an edge of that size needs before it stops being consistent with luck. - **What the answer tells you** — A journal and a statement that disagree have found something neither shows alone. A record shorter than its luck horizon cannot yet tell an edge from luck, and the check refuses below its floor rather than guess. ## Questions and answers ### What does a trading journal example look like? One row per trade: the entry and exit, the size, the reason written down before the result was known, and the result. The reason is the field that makes the trader's behaviour reviewable, because it is the one the fills cannot supply. ### Is a trading journal template or spreadsheet enough? The fields and the habit matter more than the format. A spreadsheet with one row per trade holds everything a journal needs. What any single record cannot establish is the market around the fills, which takes a second record produced outside the broker. ### What is a trading journal for? Reviewing the trader rather than the market: whether trades followed the plan, which setups were taken and which were skipped, and how the results compare with the reasons given at entry. A journal can also show the gap between the price asked for and the price filled, though not the market at that instant. ## Cite This Definition APA BibTeX HTML Hadal Instruments. (2026). Trading journal. Hadal Glossary. https://hadalinstruments.com/glossary/trading-journal/ Version dbd9b80, 2026-09-23. @misc{hadal_2026_trading-journal, author = {Hadal Instruments}, title = {Trading journal}, year = {2026}, url = {https://hadalinstruments.com/glossary/trading-journal/}, howpublished = {Hadal Glossary}, version = {dbd9b80}, note = {Pre-launch publication; version dated 2026-09-23} } Source: Hadal Instruments, Trading journal. Original Research Copy Citation **Version dbd9b80** identifies the commit that last changed this page in Hadal's content repository. That repository is not public, so the identifier does not resolve externally — it is published so a citation pins one specific state rather than a moving page. To obtain the exact version cited, use the [press and research route](https://hadalinstruments.com/press/).