diff --git a/app/models/position.py b/app/models/position.py
index 10062e0..e5ae77c 100644
--- a/app/models/position.py
+++ b/app/models/position.py
@@ -21,6 +21,8 @@ class Position:
         entry_price: Price per unit at purchase (in USD)
         entry_date: Date of position entry (for historical conversion lookups)
         entry_basis_mode: Entry basis mode ("weight" or "value_price")
+        purchase_premium: Dealer markup over spot as percentage (e.g., Decimal("0.04") for 4%)
+        bid_ask_spread: Expected sale discount below spot as percentage (e.g., Decimal("0.03") for 3%)
         notes: Optional notes about this position
         storage_cost_basis: Annual storage cost as percentage (e.g., Decimal("0.12") for 0.12%) or fixed amount
         storage_cost_period: Period for storage cost ("annual" or "monthly")
@@ -35,6 +37,8 @@ class Position:
     entry_price: Decimal
     entry_date: date
     entry_basis_mode: str = "weight"
+    purchase_premium: Decimal | None = None
+    bid_ask_spread: Decimal | None = None
     notes: str = ""
     storage_cost_basis: Decimal | None = None
     storage_cost_period: str | None = None
@@ -72,6 +76,8 @@ class Position:
             "entry_price": str(self.entry_price),
             "entry_date": self.entry_date.isoformat(),
             "entry_basis_mode": self.entry_basis_mode,
+            "purchase_premium": str(self.purchase_premium) if self.purchase_premium is not None else None,
+            "bid_ask_spread": str(self.bid_ask_spread) if self.bid_ask_spread is not None else None,
             "notes": self.notes,
             "storage_cost_basis": str(self.storage_cost_basis) if self.storage_cost_basis is not None else None,
             "storage_cost_period": self.storage_cost_period,
@@ -90,6 +96,8 @@ class Position:
             entry_price=Decimal(data["entry_price"]),
             entry_date=date.fromisoformat(data["entry_date"]),
             entry_basis_mode=data.get("entry_basis_mode", "weight"),
+            purchase_premium=(Decimal(data["purchase_premium"]) if data.get("purchase_premium") is not None else None),
+            bid_ask_spread=(Decimal(data["bid_ask_spread"]) if data.get("bid_ask_spread") is not None else None),
             notes=data.get("notes", ""),
             storage_cost_basis=(
                 Decimal(data["storage_cost_basis"]) if data.get("storage_cost_basis") is not None else None
@@ -107,6 +115,8 @@ def create_position(
     entry_price: Decimal | None = None,
     entry_date: date | None = None,
     entry_basis_mode: str = "weight",
+    purchase_premium: Decimal | None = None,
+    bid_ask_spread: Decimal | None = None,
     notes: str = "",
     storage_cost_basis: Decimal | None = None,
     storage_cost_period: str | None = None,
@@ -121,6 +131,8 @@ def create_position(
         entry_price: Entry price per unit (default: Decimal("2150"))
         entry_date: Entry date (default: today)
         entry_basis_mode: Entry basis mode (default: "weight")
+        purchase_premium: Dealer markup over spot as percentage (default: None)
+        bid_ask_spread: Expected sale discount below spot as percentage (default: None)
         notes: Optional notes
         storage_cost_basis: Annual storage cost as percentage or fixed amount (default: None)
         storage_cost_period: Period for storage cost ("annual" or "monthly", default: None)
@@ -134,6 +146,8 @@ def create_position(
         entry_price=entry_price if entry_price is not None else Decimal("2150"),
         entry_date=entry_date or date.today(),
         entry_basis_mode=entry_basis_mode,
+        purchase_premium=purchase_premium,
+        bid_ask_spread=bid_ask_spread,
         notes=notes,
         storage_cost_basis=storage_cost_basis,
         storage_cost_period=storage_cost_period,
diff --git a/app/pages/settings.py b/app/pages/settings.py
index d6d3b46..1724e2e 100644
--- a/app/pages/settings.py
+++ b/app/pages/settings.py
@@ -400,6 +400,26 @@ def settings_page(workspace_id: str) -> None:
                         label="Cost period",
                     ).classes("w-full")
 
+                    ui.separator().classes("my-3")
+                    ui.label("Premium & Spread (optional)").classes("text-sm font-semibold text-slate-700 dark:text-slate-300")
+                    ui.label("For physical gold, accounts for dealer markup and bid/ask spread.").classes("text-xs text-slate-500 dark:text-slate-400 mb-2")
+
+                    pos_purchase_premium = ui.number(
+                        "Purchase premium over spot (%)",
+                        value=0.0,
+                        min=0.0,
+                        max=100.0,
+                        step=0.1,
+                    ).classes("w-full")
+
+                    pos_bid_ask_spread = ui.number(
+                        "Bid/ask spread on exit (%)",
+                        value=0.0,
+                        min=0.0,
+                        max=100.0,
+                        step=0.1,
+                    ).classes("w-full")
+
                     with ui.row().classes("w-full gap-3 mt-4"):
                         ui.button("Cancel", on_click=lambda: add_position_dialog.close()).props("outline")
                         ui.button("Add Position", on_click=lambda: add_position_from_form()).props("color=primary")
@@ -411,6 +431,10 @@ def settings_page(workspace_id: str) -> None:
                         storage_cost_basis_val = float(pos_storage_cost_basis.value)
                         storage_cost_basis = Decimal(str(storage_cost_basis_val)) if storage_cost_basis_val > 0 else None
                         storage_cost_period = str(pos_storage_cost_period.value) if storage_cost_basis else None
+                        purchase_premium_val = float(pos_purchase_premium.value)
+                        purchase_premium = Decimal(str(purchase_premium_val / 100)) if purchase_premium_val > 0 else None
+                        bid_ask_spread_val = float(pos_bid_ask_spread.value)
+                        bid_ask_spread = Decimal(str(bid_ask_spread_val / 100)) if bid_ask_spread_val > 0 else None
 
                         new_position = Position(
                             id=uuid4(),
@@ -420,6 +444,8 @@ def settings_page(workspace_id: str) -> None:
                             entry_price=Decimal(str(pos_entry_price.value)),
                             entry_date=date.fromisoformat(str(pos_entry_date.value)),
                             entry_basis_mode="weight",
+                            purchase_premium=purchase_premium,
+                            bid_ask_spread=bid_ask_spread,
                             notes=str(pos_notes.value or ""),
                             storage_cost_basis=storage_cost_basis,
                             storage_cost_period=storage_cost_period,
diff --git a/app/services/position_costs.py b/app/services/position_costs.py
new file mode 100644
index 0000000..24941e7
--- /dev/null
+++ b/app/services/position_costs.py
@@ -0,0 +1,118 @@
+"""Position cost calculations for premium, spread, and storage costs."""
+
+from __future__ import annotations
+
+from decimal import Decimal
+from typing import Any
+
+from app.models.position import Position
+
+
+def calculate_effective_entry(
+    entry_price: Decimal,
+    purchase_premium: Decimal | None = None,
+) -> Decimal:
+    """Calculate effective entry cost including dealer premium.
+
+    Args:
+        entry_price: Spot price at entry (per unit)
+        purchase_premium: Dealer markup over spot as percentage (e.g., 0.04 for 4%)
+
+    Returns:
+        Effective entry cost per unit
+    """
+    if purchase_premium is None or purchase_premium == 0:
+        return entry_price
+    return entry_price * (Decimal("1") + purchase_premium)
+
+
+def calculate_effective_exit(
+    current_spot: Decimal,
+    bid_ask_spread: Decimal | None = None,
+) -> Decimal:
+    """Calculate effective exit value after bid/ask spread.
+
+    Args:
+        current_spot: Current spot price (per unit)
+        bid_ask_spread: Expected sale discount below spot as percentage (e.g., 0.03 for 3%)
+
+    Returns:
+        Effective exit value per unit
+    """
+    if bid_ask_spread is None or bid_ask_spread == 0:
+        return current_spot
+    return current_spot * (Decimal("1") - bid_ask_spread)
+
+
+def calculate_true_pnl(
+    position: Position,
+    current_spot: Decimal,
+) -> dict[str, Any]:
+    """Calculate true P&L accounting for premium and spread.
+
+    Args:
+        position: Position to calculate P&L for
+        current_spot: Current spot price per unit
+
+    Returns:
+        Dict with paper_pnl, realized_pnl, effective_entry, effective_exit, entry_value, exit_value
+    """
+    # Effective entry cost (includes premium)
+    effective_entry = calculate_effective_entry(position.entry_price, position.purchase_premium)
+
+    # Effective exit value (after spread)
+    effective_exit = calculate_effective_exit(current_spot, position.bid_ask_spread)
+
+    # Paper P&L (without premium/spread)
+    paper_pnl = (current_spot - position.entry_price) * position.quantity
+
+    # True P&L (with premium/spread)
+    true_pnl = (effective_exit - effective_entry) * position.quantity
+
+    # Entry and exit values
+    entry_value = position.entry_price * position.quantity
+    exit_value = current_spot * position.quantity
+
+    return {
+        "paper_pnl": float(paper_pnl),
+        "true_pnl": float(true_pnl),
+        "effective_entry": float(effective_entry),
+        "effective_exit": float(effective_exit),
+        "entry_value": float(entry_value),
+        "exit_value": float(exit_value),
+        "premium_impact": float((position.purchase_premium or 0) * entry_value),
+        "spread_impact": float((position.bid_ask_spread or 0) * exit_value),
+    }
+
+
+def get_default_premium_for_product(underlying: str, product_type: str = "default") -> Decimal | None:
+    """Get default premium/spread for common gold products.
+
+    Args:
+        underlying: Underlying instrument ("GLD", "GC=F", "XAU")
+        product_type: Product type ("default", "coin_1oz", "bar_1kg", "allocated")
+
+    Returns:
+        Tuple of (purchase_premium, bid_ask_spread) or None if not applicable
+    """
+    # GLD/GLDM: ETF is liquid, minimal spread
+    if underlying in ("GLD", "GLDM"):
+        # ETF spread is minimal, premium is 0
+        return Decimal("0"), Decimal("0.001")  # 0% premium, 0.1% spread
+
+    # GC=F: Futures roll costs are handled separately (GCF-001)
+    if underlying == "GC=F":
+        return None, None
+
+    # XAU: Physical gold
+    if underlying == "XAU":
+        defaults = {
+            "default": (Decimal("0.04"), Decimal("0.03")),  # 4% premium, 3% spread
+            "coin_1oz": (Decimal("0.04"), Decimal("0.03")),  # 1oz coins: 4% premium, 3% spread
+            "bar_1kg": (Decimal("0.015"), Decimal("0.015")),  # 1kg bars: 1.5% premium, 1.5% spread
+            "allocated": (Decimal("0.001"), Decimal("0.003")),  # Allocated: 0.1% premium, 0.3% spread
+        }
+        return defaults.get(product_type, defaults["default"])
+
+    # Unknown underlying
+    return None, None
diff --git a/tests/test_position_costs.py b/tests/test_position_costs.py
new file mode 100644
index 0000000..3268419
--- /dev/null
+++ b/tests/test_position_costs.py
@@ -0,0 +1,271 @@
+"""Tests for position cost calculations."""
+
+from __future__ import annotations
+
+from decimal import Decimal
+
+from app.models.position import Position, create_position
+from app.services.position_costs import (
+    calculate_effective_entry,
+    calculate_effective_exit,
+    calculate_true_pnl,
+    get_default_premium_for_product,
+)
+
+
+class TestEffectiveEntry:
+    """Tests for calculate_effective_entry."""
+
+    def test_no_premium_returns_entry_price(self) -> None:
+        """Entry price unchanged when no premium."""
+        result = calculate_effective_entry(Decimal("2000"), None)
+        assert result == Decimal("2000")
+
+    def test_zero_premium_returns_entry_price(self) -> None:
+        """Entry price unchanged with zero premium."""
+        result = calculate_effective_entry(Decimal("2000"), Decimal("0"))
+        assert result == Decimal("2000")
+
+    def test_premium_adds_to_entry(self) -> None:
+        """Premium adds to entry cost."""
+        # 4% premium on $2000 = $80, total $2080
+        result = calculate_effective_entry(Decimal("2000"), Decimal("0.04"))
+        assert result == Decimal("2080")
+
+    def test_large_premium(self) -> None:
+        """Large premium (10%) calculated correctly."""
+        result = calculate_effective_entry(Decimal("2000"), Decimal("0.10"))
+        assert result == Decimal("2200")
+
+
+class TestEffectiveExit:
+    """Tests for calculate_effective_exit."""
+
+    def test_no_spread_returns_spot(self) -> None:
+        """Spot unchanged when no spread."""
+        result = calculate_effective_exit(Decimal("2000"), None)
+        assert result == Decimal("2000")
+
+    def test_zero_spread_returns_spot(self) -> None:
+        """Spot unchanged with zero spread."""
+        result = calculate_effective_exit(Decimal("2000"), Decimal("0"))
+        assert result == Decimal("2000")
+
+    def test_spread_subtracts_from_exit(self) -> None:
+        """Spread subtracts from exit value."""
+        # 3% spread on $2000 = $60, result $1940
+        result = calculate_effective_exit(Decimal("2000"), Decimal("0.03"))
+        assert result == Decimal("1940")
+
+    def test_large_spread(self) -> None:
+        """Large spread (5%) calculated correctly."""
+        result = calculate_effective_exit(Decimal("2000"), Decimal("0.05"))
+        assert result == Decimal("1900")
+
+
+class TestTruePnL:
+    """Tests for calculate_true_pnl."""
+
+    def test_gld_position_no_premium_spread(self) -> None:
+        """GLD position with no premium/spread shows paper P&L equals true P&L."""
+        position = create_position(
+            underlying="GLD",
+            quantity=Decimal("100"),
+            entry_price=Decimal("400"),
+        )
+        result = calculate_true_pnl(position, Decimal("420"))
+
+        # Paper P&L: (420 - 400) * 100 = 2000
+        assert result["paper_pnl"] == 2000.0
+        assert result["true_pnl"] == 2000.0
+        assert result["effective_entry"] == 400.0
+        assert result["effective_exit"] == 420.0
+
+    def test_xau_position_with_premium(self) -> None:
+        """Physical gold position with premium shows higher effective entry."""
+        position = create_position(
+            underlying="XAU",
+            quantity=Decimal("10"),  # 10 oz
+            entry_price=Decimal("2000"),
+            purchase_premium=Decimal("0.04"),  # 4%
+        )
+        result = calculate_true_pnl(position, Decimal("2200"))
+
+        # Effective entry: 2000 * 1.04 = 2080
+        # Paper P&L: (2200 - 2000) * 10 = 2000
+        # True P&L: (2200 - 2080) * 10 = 1200
+        assert result["paper_pnl"] == 2000.0
+        assert result["true_pnl"] == 1200.0
+        assert result["effective_entry"] == 2080.0
+        assert result["premium_impact"] == 800.0  # 4% of 2000 * 10
+
+    def test_xau_position_with_spread(self) -> None:
+        """Physical gold position with spread shows lower effective exit."""
+        position = create_position(
+            underlying="XAU",
+            quantity=Decimal("10"),
+            entry_price=Decimal("2000"),
+            bid_ask_spread=Decimal("0.03"),  # 3%
+        )
+        result = calculate_true_pnl(position, Decimal("2200"))
+
+        # Effective exit: 2200 * 0.97 = 2134
+        # Paper P&L: (2200 - 2000) * 10 = 2000
+        # True P&L: (2134 - 2000) * 10 = 1340
+        assert result["paper_pnl"] == 2000.0
+        assert result["true_pnl"] == 1340.0
+        assert result["effective_exit"] == 2134.0
+        assert result["spread_impact"] == 660.0  # 3% of 2200 * 10
+
+    def test_xau_position_with_both_premium_and_spread(self) -> None:
+        """Physical gold with both premium and spread."""
+        position = create_position(
+            underlying="XAU",
+            quantity=Decimal("10"),
+            entry_price=Decimal("2000"),
+            purchase_premium=Decimal("0.04"),  # 4%
+            bid_ask_spread=Decimal("0.03"),  # 3%
+        )
+        result = calculate_true_pnl(position, Decimal("2200"))
+
+        # Effective entry: 2000 * 1.04 = 2080
+        # Effective exit: 2200 * 0.97 = 2134
+        # Paper P&L: (2200 - 2000) * 10 = 2000
+        # True P&L: (2134 - 2080) * 10 = 540
+        assert result["paper_pnl"] == 2000.0
+        assert result["true_pnl"] == 540.0
+        assert result["effective_entry"] == 2080.0
+        assert result["effective_exit"] == 2134.0
+        assert result["premium_impact"] == 800.0
+        assert result["spread_impact"] == 660.0
+
+
+class TestDefaultPremiumForProduct:
+    """Tests for get_default_premium_for_product."""
+
+    def test_gld_defaults(self) -> None:
+        """GLD has minimal premium/spread."""
+        premium, spread = get_default_premium_for_product("GLD")
+        assert premium == Decimal("0")
+        assert spread == Decimal("0.001")
+
+    def test_gldm_defaults(self) -> None:
+        """GLDM has minimal premium/spread."""
+        premium, spread = get_default_premium_for_product("GLDM")
+        assert premium == Decimal("0")
+        assert spread == Decimal("0.001")
+
+    def test_gcf_returns_none(self) -> None:
+        """GC=F futures have no premium/spread (roll costs handled separately)."""
+        result = get_default_premium_for_product("GC=F")
+        assert result == (None, None)
+
+    def test_xau_default(self) -> None:
+        """XAU default uses coin defaults."""
+        premium, spread = get_default_premium_for_product("XAU")
+        assert premium == Decimal("0.04")
+        assert spread == Decimal("0.03")
+
+    def test_xau_coin_1oz(self) -> None:
+        """XAU 1oz coins have 4%/3%."""
+        premium, spread = get_default_premium_for_product("XAU", "coin_1oz")
+        assert premium == Decimal("0.04")
+        assert spread == Decimal("0.03")
+
+    def test_xau_bar_1kg(self) -> None:
+        """XAU 1kg bars have 1.5%/1.5%."""
+        premium, spread = get_default_premium_for_product("XAU", "bar_1kg")
+        assert premium == Decimal("0.015")
+        assert spread == Decimal("0.015")
+
+    def test_xau_allocated(self) -> None:
+        """XAU allocated storage has minimal 0.1%/0.3%."""
+        premium, spread = get_default_premium_for_product("XAU", "allocated")
+        assert premium == Decimal("0.001")
+        assert spread == Decimal("0.003")
+
+    def test_unknown_underlying_returns_none(self) -> None:
+        """Unknown underlying returns None."""
+        result = get_default_premium_for_product("UNKNOWN")
+        assert result == (None, None)
+
+
+class TestPositionWithPremiumSpread:
+    """Tests for Position model with premium/spread fields."""
+
+    def test_create_position_with_premium(self) -> None:
+        """Create position with purchase premium."""
+        position = create_position(
+            underlying="XAU",
+            quantity=Decimal("10"),
+            entry_price=Decimal("2000"),
+            purchase_premium=Decimal("0.04"),
+        )
+        assert position.purchase_premium == Decimal("0.04")
+        assert position.bid_ask_spread is None
+
+    def test_create_position_with_spread(self) -> None:
+        """Create position with bid/ask spread."""
+        position = create_position(
+            underlying="XAU",
+            quantity=Decimal("10"),
+            entry_price=Decimal("2000"),
+            bid_ask_spread=Decimal("0.03"),
+        )
+        assert position.bid_ask_spread == Decimal("0.03")
+        assert position.purchase_premium is None
+
+    def test_create_position_with_both(self) -> None:
+        """Create position with both premium and spread."""
+        position = create_position(
+            underlying="XAU",
+            quantity=Decimal("10"),
+            entry_price=Decimal("2000"),
+            purchase_premium=Decimal("0.04"),
+            bid_ask_spread=Decimal("0.03"),
+        )
+        assert position.purchase_premium == Decimal("0.04")
+        assert position.bid_ask_spread == Decimal("0.03")
+
+    def test_position_serialization_with_premium_spread(self) -> None:
+        """Position serializes premium and spread correctly."""
+        position = create_position(
+            underlying="XAU",
+            quantity=Decimal("10"),
+            entry_price=Decimal("2000"),
+            purchase_premium=Decimal("0.04"),
+            bid_ask_spread=Decimal("0.03"),
+        )
+        data = position.to_dict()
+        assert data["purchase_premium"] == "0.04"
+        assert data["bid_ask_spread"] == "0.03"
+
+    def test_position_deserialization_with_premium_spread(self) -> None:
+        """Position deserializes premium and spread correctly."""
+        data = {
+            "id": "12345678-1234-5678-1234-567812345678",
+            "underlying": "XAU",
+            "quantity": "10",
+            "unit": "oz",
+            "entry_price": "2000",
+            "entry_date": "2024-01-01",
+            "purchase_premium": "0.04",
+            "bid_ask_spread": "0.03",
+        }
+        position = Position.from_dict(data)
+        assert position.purchase_premium == Decimal("0.04")
+        assert position.bid_ask_spread == Decimal("0.03")
+
+    def test_position_deserialization_without_premium_spread(self) -> None:
+        """Position deserializes without premium and spread (backward compat)."""
+        data = {
+            "id": "12345678-1234-5678-1234-567812345678",
+            "underlying": "GLD",
+            "quantity": "100",
+            "unit": "shares",
+            "entry_price": "400",
+            "entry_date": "2024-01-01",
+        }
+        position = Position.from_dict(data)
+        assert position.purchase_premium is None
+        assert position.bid_ask_spread is None