Portfolio margin estimates a portfolio’s exposure under specified scenarios. Offsetting positions may reduce the calculated requirement, but the model does not prove that realised economic risk is lower in every future event. Freed margin should be distinguished from a guaranteed hedge or loss limit.

How portfolio margin differs from fixed margin

US securities strategy-based rules, including the Reg-T framework, can recognise predefined combinations; they do not necessarily ignore every hedge. Retail CFD leverage restrictions govern other products and accounts. Portfolio margin instead uses approved scenario pricing, eligible groups, permitted offsets and minimum requirements. Comparing these regimes requires their product and account scope, rather than treating them as two names for the same system.

Under US FINRA 4210(g), eligible positions are grouped by security class and valued with an approved theoretical pricing model. Permitted offsets are applied, then the largest theoretical loss for each portfolio contributes to the account requirement, subject to minimums and other rules. Firms can impose additional requirements. It is not the worst possible future loss of every asset visible in an application.

How netting can cut the margin — a hypothetical example

Use two hypothetical linear positions: long A worth USD 100,000 and short B worth USD 80,000. Ignore costs, funding and currency changes. The following four price moves are educational scenarios, not an approved model, a broker’s tariff or proof that the positions continue to hedge each other.

Hypothetical long A USD 100,000 and short B USD 80,000: four selected scenarios
A −10%, B −10%−10,000 + 8,000 = USD −2,000
A +10%, B +10%10,000 − 8,000 = USD +2,000
A −15%, B −5%−15,000 + 4,000 = USD −11,000
A +5%, B +15%5,000 − 12,000 = USD −7,000

The largest loss among these four scenarios is USD 11,000. It does not establish an actual margin requirement without eligibility, every required scenario, permitted offsets, minimums and firm add-ons. If A falls 20% while B rises 10%, losses become USD 20,000 and USD 8,000, or USD 28,000 combined. A loss outside the selected range can exceed the earlier scenario result.

Who offers it and what the entry bar looks like

For the US service described by Interactive Brokers, upgrading an existing account requires at least USD 110,000 net liquidation value and approval for uncovered options. Below USD 100,000, margin-increasing trades are restricted. FINRA interpretation 4210(b)(4)/034 links its minimum equity floors to the firm’s monitoring capability, with higher amounts in specified circumstances. These are separate US securities-account conditions, not a worldwide threshold or automatic entitlement at every group entity.

EU retail CFD leverage restrictions apply to CFDs in their scope. Securities and options portfolio margin follow other account and product rules. Do not use a US securities margin permission as an exemption from CFD restrictions or assume all European retail risk-based margin requires professional classification. Related reading: ESMA leverage caps.

Two accounts do not automatically form one buffer

This hypothetical model has independent portfolio-margin account P and another account G at the same firm. P has USD 150,000 equity against a USD 160,000 requirement; G has USD 30,000 free cash. The total looks sufficient, but adding account screens does not remove P's shortfall.

Scroll sideways to see the full diagram

Two accounts do not automatically form one bufferP is USD 10,000 short despite USD 30,000 cash in separate account G. Adding the screens does not cover P's requirement.P: equity 150,000; required 160,000 USDP shortfall: 10,000 USDSeparate G: cash 30,000 USDG's cash is not yet P's cashCombined screens: 180,000 USDDoes not establish that P is fundedCheck transfer permission and timing
Collateral location is separate from total asset value.

US FINRA 4210(g)(6)(A) distinguishes accounts and requires a recorded transfer for a separate account's excess to cover a deficiency; it also describes a qualifying subaccount exception. For your agreement, check where assets are recognised and when a transfer takes effect. Do not assume combined buying power gives you time to react. Moving funds may reduce the other account's buffer.

Example assumptions: Fixed fictional USD amounts and independent accounts; this is not the FINRA subaccount exception. No automatic transfer or time to top up is assumed. Mechanism source: FINRA Rule 4210(g).

How equity and the margin requirement can change separately

Reducing the margin requirement does not change the exposure or P/L of unchanged positions. It can permit more buying power; increasing positions or withdrawing a needed buffer changes the resulting risk. In a hypothetical account, equity of USD 150,000 and a requirement of USD 40,000 leave USD 110,000 excess. A USD 30,000 market loss lowers equity to USD 120,000. If the requirement then rises to USD 90,000, excess falls to USD 30,000. The USD 80,000 fall in excess consists of a USD 30,000 loss and a USD 50,000 increase in collateral required; the latter is not another booked investment loss.

IBKR describes OCC’s TIMS parameters as disseminated once daily, while account compliance is updated throughout the day using current prices. This differs from claiming every model parameter is continually recalculated. Requirements can also change under firm rules. Do not assume a phone call or extra time precedes liquidation: a US securities margin agreement can allow closing without consultation. The margin call or stop out discussion must be read in its product context; risk management must track both account equity and collateral needs. The risk-management section of ForexMechanics discusses the broader planning context.

Which positions actually qualify for this model?

The described US IBKR portfolio-margin model excludes Forex positions. Other risk-based systems may cover other products, but their own specifications must be checked. Currency exposure can still be analysed economically: matched long and short positions may offset a USD leg when USD occupies the same quotation side, while remaining base-currency exposures differ. That analysis does not itself create recognised portfolio-margin offsets.

Closing a hedge can raise a requirement despite reducing total notional. In a separate hypothetical model, long A and short B each have USD 100,000 exposure and respond identically to ±15% moves. Assume full offset recognition, a chosen USD 1,000 minimum and constant equity of USD 150,000. Together, scenario P/L is zero and excess is USD 149,000. Closing B at unchanged prices leaves A with a USD 15,000 scenario loss; the model requirement becomes USD 15,000 and excess USD 135,000. Notional halves while the requirement rises. These invented rules are not FINRA rates or a broker’s offer.

Actual options and hedges can have different sensitivities, expiries and eligibility. Check the requirement for the proposed portfolio after an operation, including costs and intermediate exposure. Historical correlation or an apparently calm market does not guarantee that an offset remains effective, that margin stays low, or that a future announcement necessarily breaks it.

What to do before you reach for portfolio margin

  1. Check the actual model’s scope. List eligible products and recognised offset groups. The described US IBKR model excludes Forex; a retail CFD account uses its own national, client-category and contract rules. Neither a pair count nor a 30:1 headline establishes which model you need.
  2. Confirm account-specific eligibility. Read the broker's minimum equity, product permissions and jurisdictional classification requirements. Do not treat a US securities portfolio-margin rule as an EU CFD leverage exemption.
  3. Model changes to equity and requirements separately. Include a market loss, a higher firm requirement and the removal or expiry of a hedge. Record any chosen buffer and the liquidation rules; this does not establish a universally safe amount or guarantee time to deposit funds.
  4. Check recognised offsets and adverse scenarios. Use the model’s eligibility, grouping and sensitivities rather than historical correlation alone. Evaluate moves where a hedge works less effectively. Neither past co-movement nor a selected stress sample guarantees future protection.