How do you calculate incremental CVA when adding a new trade to an existing portfolio, and why does it differ from standalone CVA?

Incremental CVA measures the change in portfolio-level CVA caused by adding a new trade. It differs from standalone CVA because of netting: a new trade's credit exposure is calculated against the existing portfolio's net exposure, not in isolation. This means trades that offset existing exposures can actually reduce total CVA.\n\nIncremental CVA Formula:\n\nIncremental CVA = CVA(Portfolio + New Trade) - CVA(Existing Portfolio)\n\nIn practice, this requires recalculating expected exposure profiles for the combined netting set.\n\n`mermaid\ngraph TD\n A[\"Existing Portfolio
5Y payer swap, $100M\"] --> B[\"Portfolio EE Profile
Peak at Year 3\"]\n C[\"New Trade
3Y receiver swap, $60M\"] --> D[\"Standalone EE Profile
Peak at Year 1.5\"]\n B --> E[\"Combined Netting Set\"]\n D --> E\n E --> F[\"Net EE much lower
Offsetting exposures\"]\n F --> G[\"Incremental CVA << Standalone CVA\"]\n style G fill:#4ecdc4\n`\n\nWorked Example:\n\nMontrose Trading has an existing portfolio with counterparty Glenfield Corp:\n- Trade 1: 5-year payer swap, $100M notional, positive MtM of $2.8M\n\nThey want to add:\n- Trade 2: 3-year receiver swap, $60M notional\n\nGlenfield's 5-year CDS spread: 180 bps, LGD: 60%\n\nStandalone CVA of Trade 2:\n\nUsing a simplified expected exposure profile:\n\n| Year | EE (Trade 2 standalone) | Survival Prob | Default Prob | Discounted EE |\n|---|---|---|---|---|\n| 1 | $850K | 0.970 | 0.030 | $24,735 |\n| 2 | $620K | 0.941 | 0.029 | $17,146 |\n| 3 | $280K | 0.913 | 0.028 | $7,408 |\n\nStandalone CVA = LGD x Sum = 0.60 x $49,289 = $29,573\n\nIncremental CVA:\n\nWith netting, the combined exposure profile reflects offsetting positions:\n\n| Year | EE (Portfolio only) | EE (Portfolio + Trade 2) | Delta EE |\n|---|---|---|---|\n| 1 | $1,200K | $780K | -$420K |\n| 2 | $1,850K | $1,490K | -$360K |\n| 3 | $2,100K | $1,920K | -$180K |\n| 4 | $1,600K | $1,600K | $0 |\n| 5 | $900K | $900K | $0 |\n\nThe receiver swap offsets the payer swap's exposure in years 1-3. After applying default probabilities and LGD:\n\nCVA(Portfolio only) = $78,420\nCVA(Portfolio + Trade 2) = $61,180\n\nIncremental CVA = $61,180 - $78,420 = -$17,240\n\nThe new trade actually reduces CVA by $17,240 through netting benefits, despite having a $29,573 standalone CVA. This demonstrates why pricing trades at standalone CVA rather than incremental CVA leads to mispricing and suboptimal portfolio construction.\n\nPractical Implications:\n\nDesks that price at incremental CVA can offer tighter spreads on offsetting trades, winning flow that reduces overall counterparty risk. This is a key competitive advantage of dealers with diversified portfolios.\n\nExplore CVA calculation methods in our FRM Part II course.