Why this section exists
Search for prop firm rules and you get reviews. Each one lists the same figures — a profit target, a daily loss limit, a maximum drawdown — and each one implies those figures mean the same thing at every firm.
They do not. Two accounts advertising an identical "5% daily loss" can breach on different days with identical trading, because the percentage is the least interesting part of the rule. What decides the outcome is what the percentage is measured from, whether it counts unrealised profit, and when the reference level moves.
This section is written from the other side of that problem. We had to build an engine that computes pass, breach and remaining room from real accounts, which meant every one of those ambiguities had to be resolved into something a computer could execute. The pages here are that resolution, written out.
What we do not publish
No table of firm-by-firm rules, and no firm rankings. Those change without announcement, and a table of other people's rules that is right today and stale in three months is worse than no table — you would size a position on it.
What we publish instead is the shape of the rules: what varies, what the variants do to your account, and how to read your own firm's rulebook to find out which variant you have. That knowledge does not expire, and it is the part reviews skip.
Where you need a specific firm's current numbers, the only correct source is that firm's own rulebook on the day you read it.
The six principles our engine holds
These are not opinions about how firms should behave. They are the rules we had to encode to match how they do behave, and each one was a decision with a wrong answer available.
- Equity, not balance. Firms measure balance plus open floating profit. An account can be within its limits on closed trades and breached on equity at the same moment.
- Rules freeze at the start. The rulebook that applies is the one in force when the challenge began, not the one on the firm's site today.
- Time runs in the rules' timezone. Not yours and not UTC. A daily limit resets at a specific local time in a specific city, and trading either side of it lands in different days.
- Deposits and withdrawals are not profit. They must be excluded from the target and from the daily loss — but they do move the drawdown floor, because drawdown measures capital rather than earnings. The two treatments are deliberately different.
- The engine reads a clock passed to it. Nothing computes from "now" internally, so the same inputs always produce the same answer and yesterday's state can be recomputed exactly.
- Mirror, not oracle. The output is "your limit is 87% used", never "do not trade". The one exception is a hard news window, where the mechanics are not a matter of opinion.
Where to start
What a rulebook actually contains — the parameters that genuinely differ between firms, and the ones that only look different.
What breaches an account — the four drawdown shapes, why an intraday floor cannot be computed exactly from end-of-day data, and the ordering rule that decides whether a record day can also be a breach day.
Equity versus balance — the distinction underneath most surprise failures, and why a withdrawal is not a loss but still changes what you can lose.
Passing a challenge — target basis, what counts as a trading day, and the three qualifiers firms use to stop people clicking a button ten times.
Payouts and the consistency rule — the rule most likely to hold money you have already made, and the difference between one that blocks a payout and one that blocks a pass.