Durable reference map
A three-stage method to reuse whenever conditions change
Keep the sequence of inputs, calculation and exception testing stable instead of relying on a market forecast.
- Align inputs and unitsGo to equations and definitionsRemaining quantity・Realized gross P&L from partial exits・Combined result if the remainder stops
- Reconcile the worked exampleGo to table and calculation stepsTwo stop conditions after exiting 0.40 lot of a 1.00-lot position at 104
- Test exceptions and next checksGo to rules and counterexampleDerive remaining quantity by subtracting confirmed exit fills from confirmed initial fills.
A scale-out creates two P&L states
The executed 0.40-lot exit becomes realized P&L while the other 0.60 lot remains exposed to price changes. Treating the whole position as closed, or returning the realized portion to unrealized P&L, breaks both quantity and P&L reconciliation.
Link the parent position to each exit execution, quantity, price, time and residual quantity. In a netting account, also verify that the opposite-side fill was recorded as a reduction rather than a new position.
- The initial, exited and remaining quantity identity
- Separate realized and unrealized fields
- Separate gross and net values
Calculate realized P&L only on exited quantity
For a 1.00-lot long entered at 100, an executed 0.40-lot exit at 104 and a multiplier of USD 100 per price unit per lot produce 0.40 × (104 − 100) × 100 = USD 160 realized gross P&L. Do not add the 0.60-lot remainder’s unrealized gain in advance.
FIFO, average-cost and specific-lot rules can assign a different entry cost to the exit. Preserve the account’s cost-basis rule and the price used for reconciliation.
Revalue the remainder to its stop
If the 0.60-lot remainder exits at an assumed 98, residual P&L relative to the 100 entry is 0.60 × (98 − 100) × 100 = −USD 120. Combining that with USD 160 realized gross P&L and subtracting USD 12 total charges gives +USD 28.
At a stress exit of 95, residual P&L is −USD 300 and the combined result becomes −USD 152 despite the same realized gain. Safety comes from remaining quantity and an executable exit condition, not from the phrase “took partial profit”.
- +USD 28 at the base 98 exit
- −USD 152 at the stress 95 exit
- USD 12 total charges deducted in both
Reserve charges before the final exit
Use actual entry and partial-exit charges already incurred, then reserve future charges for closing the residual position under an explicit assumption. Do not deduct spread cost a second time when it is already embedded in fill records.
When P&L currency differs from account currency, apply Article 12‘s loss-side conversion factor and timestamp before combining the amounts.
- Separate incurred from future charges
- Show gross, charges and net in one currency
- Check which costs an API field already includes
Boundary with an unfilled entry remainder
Article 13 covers an entry that has only partially filled and may still have a live unfilled balance. Here the initial position existed and the 0.40-lot exit is confirmed; the remaining 0.60 lot is a holding, not an unfilled order.
- Use Article 13 for a live entry remainder
- Use this article for a holding after a confirmed partial exit
Test break-even execution separately
The +USD 28 result is arithmetic conditioned on an exit at 98. Article 15 addresses why moving a stop to the 100 entry does not guarantee zero P&L after spread, charges, adverse execution or a gap. This article does not generalize a submitted stop price into an assured fill price.
Calculation framework
Remaining quantity
Read the role of each equation first, then follow the numerical example to check the decision path.
Remaining quantity
Q_remaining = Q_initial − Σ Q_exit- Q_initial: confirmed initial position quantity
- Q_exit: each deduplicated partial-exit fill quantity
In plain language: Subtract only confirmed exit executions from the established position.
When this conclusion does not apply: Calculate only with non-negative Q_initial and Q_exit values on one quantity basis and ΣQ_exit ≤ Q_initial. Exclude canceled, rejected or unfilled exit orders.
Realized gross P&L from partial exits
PnL_realized = Σ(Q_exit × side × (P_exit − P_entry) × M)- P_exit: each partial-exit fill price
- P_entry: entry or cost-basis price used for price P&L; charges embedded here are excluded from C_total
- M: currency value per price unit per lot
- side: +1 for a long position and −1 for a short position
In plain language: Convert the price change on exited quantity only into currency P&L.
When this conclusion does not apply: Calculate only with non-negative Q_exit values, M > 0, side fixed as +1 or −1, and prices and M aligned to one currency and price unit, using the account’s applicable cost-basis rule.
Combined result if the remainder stops
PnL_if_stopped = PnL_realized + Q_remaining × side × (P_stop − P_entry) × M − C_total- P_stop: assumed exit price for the remaining quantity
- C_total: total entry, partial-exit and residual-exit charges not already embedded in P_entry
- side: +1 for a long position and −1 for a short position
In plain language: Combine realized P&L, residual P&L and charges into one conditional whole-position result.
When this conclusion does not apply: Calculate only when 0 ≤ Q_remaining ≤ Q_initial, M > 0, C_total ≥ 0, and side, price and currency bases are known. Exclude charges embedded in P_entry from C_total; the expression does not guarantee stop execution.
Recognize that a scale-out creates realized and open states
A confirmed partial exit converts P&L on the exited quantity into realized P&L while leaving the residual quantity exposed to future price changes. Treating the full original position as closed omits open risk; treating the realized exit as still unrealized breaks accounting. Both states must remain linked to one parent position.
In the hypothetical long, 1.00 lot was established at 100 and 0.40 lot exits at 104. The confirmed residual is 0.60 lot. That quantity is a holding, not an unfilled entry order, and it needs its own current stop, executable-price assumption, costs, and currency treatment.
The event log should identify each initial and exit fill, quantity, price, time, and position action. In a netting account, an opposite-side execution may reduce rather than open a new position. Provider state and parent linkage determine the accounting, not the order verb alone.
Calculate realized P&L only on exited quantity
For the long example, 0.40 times the price change from 100 to 104 times USD 100 per price unit per lot gives USD 160 realized gross P&L. Applying the four-point gain to the full 1.00 lot would create USD 400 and recognize profit that remains dependent on the open 0.60 lot.
Cost-basis rules can alter which entry price belongs to an exit when several lots were acquired. FIFO, average cost, and specific-lot methods should not be interchanged after the result is known. The record must retain the account’s applicable method and the fill prices used for reconciliation.
Gross P&L excludes charges. Entry and partial-exit fees already incurred should be recorded separately or embedded consistently in the cost basis. The label “realized” must not imply net account value until every included cost and required currency conversion is stated.
Revalue the residual position to a stated executable scenario
At an assumed exit of 98, the 0.60-lot remainder loses 0.60 times two price units times USD 100, or USD 120. This is conditional residual P&L, not yet realized and not guaranteed by a stop trigger. The selected price should be labeled as an execution assumption.
Combining USD 160 realized gross with negative USD 120 residual P&L and USD 12 total charges gives positive USD 28. At the separate stress exit of 95, residual P&L is negative USD 300 and the combined result is negative USD 152. The realized gain is identical in both cases.
The contrast shows why taking partial profit does not create a loss boundary. Safety depends on remaining quantity, adverse executable price, charges, and conversion. A favorable realized component can be outweighed by residual loss when the market moves farther or fills worse than the submitted stop.
A scenario ladder can vary only the residual executable price while retaining the realized USD 160, 0.60-lot remainder, multiplier, and charges. That controlled view identifies the point where combined P&L changes sign without implying that any rung is a forecast or guaranteed fill.
Keep quantity reconciliation ahead of P&L aggregation
Remaining quantity equals confirmed initial fills minus confirmed exit fills. Canceled, rejected, or unfilled exit orders do not reduce the position. A cancel request or displayed order ticket should not change exposure until an authoritative execution or position event confirms the reduction.
The sum of exits cannot exceed the established position on the same quantity basis unless the account has crossed into a new opposite position. Clipping a negative remainder to zero would hide that state change. The ledger should resolve whether fills closed, reduced, or opened exposure before applying the scale-out formula.
Partial fills of the exit require weighted prices and cumulative reconciliation just like an entry. Duplicate events can overstate realized P&L and understate remaining risk simultaneously. Unique execution IDs and a parent-position balance are therefore central risk controls, not merely bookkeeping details.
The quantity invariant is initial confirmed fills minus confirmed reductions equals current position, subject to any documented reversal into a new opposite holding. It should be checked before money is aggregated. A clean USD result cannot compensate for a residual quantity that fails this identity.
Reserve costs for the residual exit without counting them twice
The USD 12 total should identify actual entry and partial-exit charges plus an explicit estimate for closing the remainder. If spread is already embedded in fill prices, subtracting a separate spread field again duplicates it. Each cost needs an inclusion flag, currency, timestamp, and relation to quantity.
Future charges may depend on the residual 0.60 lot and holding period. A fixed reserve can be added directly, while per-lot or nonlinear fees need calculation at the scenario quantity. Unknown financing should be presented as a range or unresolved input rather than set to zero because the position is currently profitable.
When P&L and fees originate in another currency, convert them to account currency on a documented path before summing. Entry-time, partial-exit, and residual-exit factors can differ. One later rate should not be applied retroactively to make the whole lifecycle look internally uniform.
A conversion bridge can retain each component in its original currency and show the factor that produced the account amount. This makes the USD 12 charge assumption auditable and prevents a favorable later exchange rate from being backfilled across entry and exit merely to improve the combined result.
Distinguish scale-out from a partially filled entry
A partially filled entry has a confirmed position plus a possible live remainder that can add exposure. A scale-out begins with an established position and a confirmed exit that removes exposure. The same 0.60-lot number can therefore represent a holding in one case and an unfilled intention in another.
The accounting consequence is opposite. A live entry remainder needs conditional reserve until cancellation; a residual holding needs open-stop risk until exit. Treating the scale-out remainder as unfilled can release real exposure, while treating an unfilled entry balance as held can overstate current P&L.
Parent intent, provider position action, and execution IDs should determine classification. A user label such as “partial” is insufficient because it describes both workflows. The audit record should name entry fill, exit fill, remaining position, and remaining order as separate quantities.
Do not let a break-even label erase residual loss
Moving the residual stop to entry changes the trigger, not the guarantee of execution. A sell stop can fill below entry in a fast market or after a gap, and charges can keep the net result negative even with no price difference. The residual estimate should use an adverse executable-price scenario and explicit costs.
The positive USD 28 row assumes an exit at 98, not at entry. It therefore cannot be generalized into proof that a partial profit protects the entire trade. A separate break-even analysis should hold the current 0.60 quantity and test routine adverse fill, gap conditions, and costs without netting realized profit until both components are independently calculated.
If residual quantity reaches zero through confirmed exits, no further position stop-loss calculation is needed. Other charges can remain in their ledger. This boundary is based on position state, not on a platform button or the hope that the next fill occurs at the displayed stop.
Preserve side and cost-basis rules across the lifecycle
The formula uses side plus one for a long and minus one for a short so favorable and adverse price changes retain the correct sign. Prices, multiplier, and quantities must share one contract basis. Applying absolute differences would turn a residual loss into a gain or make every exit appear favorable.
When entries occur at several prices, the cost-basis method determines the reference for realized and remaining P&L. It should be set by the account or analysis policy before exits are reviewed. Switching methods after a favorable partial exit can reassign gains between realized and unrealized states without changing total economics.
Tax reporting can use rules beyond this educational model. The article’s combined result is an operational account-currency reconstruction, not tax advice or an official statement. Provider records should be reconciled, and any difference in basis or fee treatment should remain visible rather than forced into the simplified formula.
Attack the lifecycle with duplicate and unfilled exits
A duplicate 0.40 exit event should not reduce remaining quantity to 0.20 or double realized P&L. An exit order that is submitted but unfilled should leave the position at 1.00 lot. These tests catch systems that infer economic state from requested quantity rather than unique confirmed executions.
A stress test fills only part of the 0.40 exit and checks that realized P&L and residual quantity use the executed amount. Another changes cost basis and verifies that the report creates a new scenario rather than overwriting the account rule. A short-position test reverses side while preserving nonnegative quantity.
Boundary cases include exits exceeding the initial position, negative charges, zero multiplier, unknown entry, and mixed currencies. The correct response is unresolved, not a clipped or absolute-valued result. A clean combined number from contradictory state would be more misleading than an explicit reconciliation failure.
Monitor residual risk after every confirmed amendment
A new partial exit changes remaining quantity and future exit charges, so residual stop risk must be recomputed. A stop amendment changes the adverse scenario. A conversion or specification update can change account-currency value. The record should version each event and show which one altered the combined conditional result.
A favorable price move can reduce an executable loss estimate, but unrealized profit should not automatically become budget for another order unless an explicit portfolio policy permits it. Expected profit is not negative risk. Aggregate daily and portfolio constraints need current open exposure rather than the phrase that some profit was already taken.
If the stop is canceled or rejected, the model should not continue displaying the previous protected scenario as active. It should flag missing protection and withhold any claim about a defined exit. Operational state can dominate the arithmetic even when remaining quantity and cost basis are correct.
Build a position ledger that can reproduce the two scenarios
The parent record needs confirmed initial fills, entry basis, side, multiplier, account and profit currencies, cost-basis method, and position ID. Exit rows need unique IDs, quantities, prices, timestamps, fees, and provider actions. Derived remaining quantity and realized gross P&L should reconcile to these events.
Scenario rows add assumed residual executable price, stop order state, future charges, conversion, residual P&L, and combined net result. The 98 and 95 cases must share the same 0.60 lot and USD 160 realized component so the comparison isolates the residual exit assumption.
Outcome reconciliation later appends actual residual fills without replacing either scenario. Keeping plan and outcome separate allows analysts to assess how conservative the assumptions were. It also prevents the final realized result from being presented as though it had been known when the scale-out occurred.
Review should compare scenario error across a full cohort rather than celebrate one accurate row. A better fill than 98 does not prove residual risk was zero, and a worse fill does not establish that 95 is a universal stress. Each observation remains tied to its product, session, order method, and protection state.
Use partial profits in aggregate capacity only after state is clear
Realized net profit can affect account equity, but a daily non-replenishing policy may still refuse to restore consumed loss capacity. Open risk on the 0.60 lot remains separate. The scale-out ledger should feed these controls with realized and open components rather than one net phrase such as secured profit.
A portfolio system can choose a different replenishment rule, but it must be declared before the result and capped explicitly. Opportunistically using realized gains to enlarge new orders while ignoring residual downside can create exposure beyond the original parent budget. The policy should not change because the first exit was favorable.
Margin released by the partial exit is also not the same as loss budget released. Lower required margin can enable an order operationally while price-distance capacity remains constrained. Displaying both prevents the scale-out from being misread as automatic permission for a larger new position.
Interpret transaction and fee sources within scope
OANDA transaction definitions support distinguishing trades opened, reduced, and closed, as well as VWAP, spread-cost, and conversion fields. Interactive Brokers material supports separating unrealized P&L on an open position from realized P&L after sale. Investor.gov supports the general conclusion that transaction costs reduce value.
These sources do not provide the 100 entry, 104 partial exit, 98 or 95 scenarios, USD 100 multiplier, or USD 12 charges. Those values are hypothetical. Provider cost-basis and account rules can differ, so the production reconstruction must follow current statements and transaction schemas.
The evidence-backed claim is the state separation, not a forecast of profit. A partial exit realizes one component while the remainder stays exposed and costs reduce the combination. The specific plus USD 28 and minus USD 152 values are derived arithmetic under two declared executable-price assumptions.
State the scale-out conclusion with its conditional price
After the confirmed 0.40-lot exit, remaining quantity is 0.60 lot and realized gross P&L is USD 160 under the hypothetical multiplier. At an assumed 98 residual exit, combined net result after USD 12 charges is plus USD 28. At 95, it is minus USD 152. Both results depend on the stated executable-price scenario.
The unchanged realized profit does not determine whether the whole position remains positive. Residual quantity, actual executable exit, costs, side, basis, and conversion do. The decision consequence is to keep open risk and realized P&L separate until each has been calculated and then combine them on one currency basis.
This is educational accounting, not a recommendation to scale out or a promise that a stop will fill. It shows why partial profit does not erase remaining loss and why a favorable first exit should not become an undocumented budget multiplier for another order.
A final verifier should recompute remaining quantity, realized gross P&L, residual scenario P&L, and costs in that order. It should fail closed when side, basis, or currency is missing. The combined number is trustworthy only after every component reconciles to the same parent position and unit system.
Decision and control rules
- Derive remaining quantity by subtracting confirmed exit fills from confirmed initial fills.
- Separate realized gross P&L, residual stop P&L and total charges before combining them.
- Do not set residual risk to zero merely because a partial profit was taken.
- Record cost-basis method, currency conversion and cost-field inclusions.
- State the stop-versus-fill limitation and add Article 15 stress assumptions when needed.
Common failure modes
- Applying the 0.40-lot realized profit to the full 1.00 lot
- Leaving remaining quantity at 1.00 lot after the exit
- Adding unrealized P&L to a reinvestment budget as though realized
- Ignoring or double-counting commissions and spread costs
- Assuming a stop moved to entry guarantees non-negative total P&L
Evidence and specifications
- OANDA v20 REST API — Transaction Definitions
What this source supports: OANDA’s OrderFillTransaction distinguishes tradeOpened, tradeReduced, tradesClosed, fullVWAP, halfSpreadCost and homeConversionFactors, supporting reconstruction of partial exits, prices and costs from fill records.
- IBKR Campus — Unrealized P&L
What this source supports: IBKR distinguishes unrealized P&L on an open position from P&L realized after sale and notes associated fees and commissions, supporting separate treatment after a partial exit.
- Investor.gov — Updated Investor Bulletin: How Fees and Expenses Affect Your Investment Portfolio
What this source supports: The SEC’s Investor.gov explains that costs including transaction fees reduce investment value, supporting deduction of entry, partial-exit and residual-exit costs from a scale-out result.
Questions to resolve
Does exiting 0.40 lot reduce risk by exactly 40%?
Residual price risk scales with quantity if stop distance and contract value stay unchanged, but stop changes, costs, currency conversion and gaps can prevent a simple 40% whole-result reduction.
Can realized profit fund more risk on the remainder?
First display realized net P&L, residual stop loss and future costs in the same currency and time basis. Whether to create a new budget is a separate policy; this article does not recommend automatic reinvestment.
Why can broker realized P&L differ from my calculation?
Average-cost, FIFO or lot-selection rules, commissions, conversion times and daily resets can differ. Reconcile execution history with the field definition.
What is the smallest distinction from Article 13?
Article 13‘s remainder is an entry quantity that has not filled. Here the remainder is an established holding left after a confirmed partial exit.
Recalculate from current inputs
Enter initial, exited and remaining quantities plus realized P&L and charges separately in the Lot Size Calculator, then recalculate the residual stop condition.
Important: This educational example checks quantity and P&L after a scale-out. Prices, multipliers, cost-basis rules, charges, tax treatment and stop execution vary by product and account; no profit or loss ceiling is guaranteed.