What Is the Difference Between a House Margin Requirement and a Regulation T Requirement?
Two investors buying the identical stock, on margin, at the same brokerage can end up facing different collateral requirements — not because of anything unusual in their accounts, but because of what they’re holding.
The short answer
A house margin requirement is a brokerage firm’s own internal collateral standard, which can be set higher than the federal minimum established under Regulation T. Firms are free to require more of an investor’s own money relative to borrowed funds than the law mandates, and they routinely do so for positions the firm considers riskier, even though they’re never allowed to require less than the federal floor.
Why brokers set their own, stricter rules
Regulation T establishes a baseline that applies broadly, but it isn’t built around the specific risk of any one broker’s customer base or any one security. Firms carry the actual lending risk on margin balances, so many set house requirements calibrated to their own comfort with that risk, layered on top of the federal minimum rather than replacing it. This gives firms room to respond to conditions the federal rule doesn’t address directly.
What tends to push a house requirement higher
Several characteristics commonly lead a broker to require more collateral than the regulatory floor:
- Volatility. Securities that swing widely in price carry more risk of a sudden collateral shortfall, so brokers often require a bigger cushion against them.
- Concentration. A position representing a large share of an account’s total value can trigger a stricter requirement, since there’s less diversification to absorb a decline.
- Low-priced or thinly traded securities. Stocks that are harder to sell quickly at a stable price are frequently subject to higher house requirements or excluded from margin eligibility altogether.
- Market conditions. During periods of unusual volatility across markets generally, firms sometimes raise house requirements broadly, not just for individual securities.
How this plays out for an account
Because house requirements sit above the Regulation T floor, they affect both how much can initially be borrowed against a position and, separately, how much equity must be maintained afterward as prices move. A firm can also change its house requirements on existing positions, not just new ones, which means the terms an investor opened a position under aren’t necessarily fixed for as long as the position is held.
Why this matters when a call happens
When a margin call is triggered, it’s worth knowing whether it’s driven by the federal minimum or by a firm’s own stricter standard, since the latter can shift with little warning based on the firm’s own risk assessment rather than a change in the law. Two accounts holding the same security at different brokers, or even the same broker at different times, aren’t guaranteed to face identical requirements.
A useful habit
Checking a broker’s current margin agreement, rather than assuming the federal minimum is the only number that applies, is the clearest way to understand what a house requirement could mean for a specific position before relying on borrowed funds to hold it.