The Martingale Rule
A precise mathematical strategy turned into a vague catch-all that can get you breached for adding a single lot to a losing position.
What Martingale actually is
Martingale is a specific strategy: double your position size after every loss until a winning trade recovers everything. Origin: 18th century gambling theory. Outcome: works perfectly until the losing streak that wipes the account, which is mathematically guaranteed to arrive eventually. It is a legitimate concept with a clear definition: you keep doubling until you recover.
That definition matters, because most prop firm "martingale rules" don't use it. Nick Leeson brought down Barings Bank in 1995 doing exactly this: doubling futures positions to recover hidden losses until the hole was too large to fill. The bank had been operating since 1762. It took one martingale spiral 28 days to end it.
How firms stretch the word
Scaling into a position, adding to a trade while it moves against you, is a standard technique used by traders across every style and timeframe. It has nothing to do with doubling-until-recovery. But because it involves increasing position size while in a loss, firms with loose definitions classify it as martingale. The word gets applied to any behaviour they find inconvenient, with "martingale" as the justification for payout denial.
The spectrum of how firms define it
Stupidly strict: any addition to a losing position
Blue Guardian had a version of this: opening 1 lot and adding 0.01 lot to the same trade was classified as a breach. The additional position didn't need to be large, it just needed to exist while the original was in a loss. This rule is gone, likely because the firm noticed it was catching normal trading. But it illustrates how broadly the word can be applied when there's no precise definition anchoring it.
Moderate: no same-size or multiplier additions
Some firms allow scaling in but restrict the sizing: you cannot add a position equal to or larger than your original. So 1 lot + 0.5 lot may be fine, 1 lot + 1 lot is a breach. This at least allows some scaling while targeting the actual doubling behaviour. Still catches traders who legitimately scale in equal sizes as part of their normal approach.
Outcome-based: the math needs to make sense
The more reasonable approach: scale in however you want, but the risk-reward has to justify it. Scaling in at -10 pips and targeting average +1 pip is a breach. You're piling into a bad position hoping for a tiny recovery. Scaling in at -10 pips to a technical level with a target 40 pips away is fine. The firm is looking at intent and outcome, not just whether a second position was opened while the first was red.
The two sides
The firm's argument
True martingale is genuinely dangerous and statistically guaranteed to blow an account given enough time. Firms don't want traders who recover losses by stacking size. It creates sudden large drawdowns and distorts the risk profile of the account.
The trader's reality
Scaling into a position at a better price is not martingale. It's position management. A trader who adds to a long at a technical support level with a defined stop below it is taking a second trade, not doubling down on a gamble. Loose definitions that can't distinguish between these two things will eventually catch normal traders and deny legitimate payouts.