phase 6: uk cgt calculator

atlas-terminal/apps/web/src/app/portfolio/page.tsx

@@ -2,6 +2,7 @@
 import { useState, useEffect } from "react";
 import { AlertTriangle, Check, CheckCircle2, CircleX, Pencil, Trash2 } from "lucide-react";
 import { CorrelationMatrix } from "../components/portfolio/CorrelationMatrix";
+import { flags } from "../lib/flags";
 
 interface Position {
   id?: string;
@@ -298,16 +299,23 @@ export default function PortfolioPage() {
     <div>
       <div className="portfolio-header">
         <h1 className="text-2xl font-bold">Portfolio</h1>
-        <div className="currency-toggle">
-          {["USD", "GBP", "KRW", "EUR", "JPY"].map((cur) => (
-            <button
-              key={cur}
-              className={`currency-btn ${displayCurrency === cur ? "active" : ""}`}
-              onClick={() => setDisplayCurrency(cur)}
-            >
-              {getCurrencySymbol(cur)} {cur}
-            </button>
-          ))}
+        <div className="flex flex-wrap items-center gap-2">
+          {flags.cgt && (
+            <a href="/portfolio/tax" className="rounded border border-brand-gold bg-brand-gold/15 px-3 py-2 text-xs font-semibold text-brand-navy hover:bg-brand-gold/25">
+              UK CGT
+            </a>
+          )}
+          <div className="currency-toggle">
+            {["USD", "GBP", "KRW", "EUR", "JPY"].map((cur) => (
+              <button
+                key={cur}
+                className={`currency-btn ${displayCurrency === cur ? "active" : ""}`}
+                onClick={() => setDisplayCurrency(cur)}
+              >
+                {getCurrencySymbol(cur)} {cur}
+              </button>
+            ))}
+          </div>
         </div>
       </div>
 

atlas-terminal/apps/web/src/app/portfolio/tax/page.tsx

@@ -0,0 +1,163 @@
+"use client";
+
+import { useState } from "react";
+import { ErrorBanner } from "../../components/ui/ErrorBanner";
+import { LoadingPulse } from "../../components/ui/LoadingPulse";
+import { StatCard } from "../../components/ui/StatCard";
+import { flags } from "../../lib/flags";
+import { useApi } from "../../lib/use-api";
+
+type IncomeBand = "basic" | "higher";
+
+interface CgtPosition {
+  ticker: string;
+  quantity: number;
+  avg_price: number;
+  current_price: number;
+  cost_currency: string;
+  current_currency: string;
+  cost_gbp: number;
+  value_gbp: number;
+  gain_gbp: number;
+  gain_per_share_gbp: number;
+}
+
+interface OptimalRealization {
+  ticker: string;
+  shares_to_sell: number;
+  estimated_gain_gbp: number;
+}
+
+interface CgtResponse {
+  income_band: IncomeBand;
+  total_unrealized_gain_gbp: number;
+  allowance: number;
+  allowance_remaining: number;
+  taxable_if_sold_all: number;
+  tax_if_sold_all: number;
+  rate: number;
+  optimal_realization: OptimalRealization[];
+  positions: CgtPosition[];
+  tax_year_end: string;
+  fx_source: string;
+  disclaimer: string;
+}
+
+function gbp(value: number): string {
+  return `£${value.toLocaleString(undefined, { minimumFractionDigits: 0, maximumFractionDigits: 0 })}`;
+}
+
+function statusFor(data: CgtResponse | null): { label: string; tone: "positive" | "negative" | "accent" } {
+  if (!data) return { label: "—", tone: "accent" };
+  if (data.total_unrealized_gain_gbp <= data.allowance * 0.75) return { label: "Under allowance", tone: "positive" };
+  if (data.total_unrealized_gain_gbp <= data.allowance) return { label: "Approaching limit", tone: "accent" };
+  return { label: "Allowance exceeded", tone: "negative" };
+}
+
+export default function PortfolioTaxPage() {
+  const [incomeBand, setIncomeBand] = useState<IncomeBand>("higher");
+  const url = flags.cgt ? `/api/tax/uk/cgt/local?income_band=${incomeBand}` : null;
+  const { data, loading, error } = useApi<CgtResponse>(url, { cacheTtlMs: 60_000 });
+  const status = statusFor(data);
+
+  if (!flags.cgt) {
+    return (
+      <div className="atlas-page">
+        <ErrorBanner variant="info" message="UK CGT calculator is disabled. Set NEXT_PUBLIC_FLAG_CGT=true to enable it." />
+      </div>
+    );
+  }
+
+  return (
+    <div className="atlas-page">
+      <div className="mb-6 flex flex-wrap items-start justify-between gap-3">
+        <div>
+          <h1 className="font-serif text-3xl font-bold text-brand-navy">UK CGT Calculator</h1>
+          <p className="mt-1 text-sm text-text-secondary">Allowance simulation for current portfolio positions.</p>
+        </div>
+        <div className="flex gap-2">
+          {(["basic", "higher"] as IncomeBand[]).map((band) => (
+            <button
+              key={band}
+              type="button"
+              onClick={() => setIncomeBand(band)}
+              className={`rounded border px-4 py-2 text-xs font-semibold capitalize ${incomeBand === band ? "border-brand-navy bg-brand-navy text-white" : "border-border text-text-secondary hover:bg-surface-sunken"}`}
+            >
+              {band} rate
+            </button>
+          ))}
+        </div>
+      </div>
+
+      <ErrorBanner variant="warning" message="Not tax advice. This uses static FX estimates and simplified Section 104 pooling assumptions. Check HMRC guidance before acting." className="mb-5" />
+      <ErrorBanner variant="error" message={error} className="mb-5" />
+
+      {loading ? <LoadingPulse height="h-48" label="Calculating CGT..." /> : (
+        <>
+          <div className="mb-6 grid grid-cols-1 gap-3 md:grid-cols-4">
+            <StatCard label="Status" value={status.label} tone={status.tone} />
+            <StatCard label="Unrealized Gain" value={data ? gbp(data.total_unrealized_gain_gbp) : "—"} />
+            <StatCard label="Allowance Left" value={data ? gbp(data.allowance_remaining) : "—"} tone={data && data.allowance_remaining <= 0 ? "negative" : "positive"} />
+            <StatCard label="Tax If Sold All" value={data ? gbp(data.tax_if_sold_all) : "—"} tone={data && data.tax_if_sold_all > 0 ? "negative" : "default"} />
+          </div>
+
+          <section className="atlas-card mb-6">
+            <header className="border-b border-border px-5 py-4">
+              <h2 className="font-serif text-lg font-bold text-brand-navy">Allowance Use Plan</h2>
+              <p className="mt-1 text-xs text-text-muted">Greedy estimate of sales that could use the annual allowance without exceeding it.</p>
+            </header>
+            <div className="p-5">
+              {data?.optimal_realization.length ? (
+                <div className="grid grid-cols-1 gap-3 md:grid-cols-2 xl:grid-cols-3">
+                  {data.optimal_realization.map((item) => (
+                    <div key={item.ticker} className="rounded-md border border-border bg-surface-sunken p-4">
+                      <div className="font-mono text-lg font-bold text-brand-navy">{item.ticker}</div>
+                      <div className="mt-2 text-sm text-text-secondary">
+                        Sell <span className="font-mono text-text-primary">{item.shares_to_sell.toLocaleString()}</span> shares for about <span className="font-mono text-fin-positive">{gbp(item.estimated_gain_gbp)}</span> gain.
+                      </div>
+                    </div>
+                  ))}
+                </div>
+              ) : (
+                <div className="text-sm text-text-muted">No positive gains available to realize against the allowance.</div>
+              )}
+            </div>
+          </section>
+
+          <section className="atlas-table-shell">
+            <div className="border-b border-border px-5 py-4">
+              <h2 className="font-serif text-lg font-bold text-brand-navy">Position Gains</h2>
+              <p className="mt-1 text-xs text-text-muted">FX source: {data?.fx_source || "—"} · Tax year end: {data?.tax_year_end || "—"}</p>
+            </div>
+            <div className="overflow-x-auto">
+              <table className="w-full min-w-[860px] text-sm">
+                <thead className="bg-surface-sunken">
+                  <tr className="border-y border-border-strong text-[11px] uppercase tracking-[0.12em] text-brand-navy">
+                    <th className="px-5 py-3 text-left font-semibold">Ticker</th>
+                    <th className="px-3 py-3 text-right font-semibold">Qty</th>
+                    <th className="px-3 py-3 text-right font-semibold">Cost</th>
+                    <th className="px-3 py-3 text-right font-semibold">Value</th>
+                    <th className="px-3 py-3 text-right font-semibold">Gain</th>
+                    <th className="px-5 py-3 text-right font-semibold">Gain / Share</th>
+                  </tr>
+                </thead>
+                <tbody>
+                  {(data?.positions || []).map((position) => (
+                    <tr key={position.ticker} className="border-b border-border/60 hover:bg-surface-sunken">
+                      <td className="px-5 py-3 font-mono font-bold text-brand-navy">{position.ticker}</td>
+                      <td className="px-3 py-3 text-right font-mono tabular-nums text-text-primary">{position.quantity.toLocaleString()}</td>
+                      <td className="px-3 py-3 text-right font-mono tabular-nums text-text-secondary">{gbp(position.cost_gbp)}</td>
+                      <td className="px-3 py-3 text-right font-mono tabular-nums text-text-secondary">{gbp(position.value_gbp)}</td>
+                      <td className={`px-3 py-3 text-right font-mono tabular-nums ${position.gain_gbp >= 0 ? "text-fin-positive" : "text-fin-negative"}`}>{gbp(position.gain_gbp)}</td>
+                      <td className="px-5 py-3 text-right font-mono tabular-nums text-text-primary">£{position.gain_per_share_gbp.toFixed(4)}</td>
+                    </tr>
+                  ))}
+                </tbody>
+              </table>
+            </div>
+          </section>
+        </>
+      )}
+    </div>
+  );
+}

atlas-terminal/server/main.py

@@ -81,7 +81,7 @@ app.add_middleware(
 )
 
 # --- Mount routers ---
-from server.routers import edgar, analysis, valuation, market_data, news, crypto, fx, portfolio, technical, financials, estimates, earnings, insider, screener, markets, fmp, macro, dart, edinet, research, chat, copilot, credentials, calendar  # noqa: E402
+from server.routers import edgar, analysis, valuation, market_data, news, crypto, fx, portfolio, technical, financials, estimates, earnings, insider, screener, markets, fmp, macro, dart, edinet, research, chat, copilot, credentials, calendar, tax  # noqa: E402
 
 app.include_router(edgar.router, prefix="/api/edgar", tags=["SEC EDGAR"])
 app.include_router(analysis.router, prefix="/api/analysis", tags=["AI Analysis"])
@@ -107,6 +107,7 @@ app.include_router(chat.router, prefix="/api/chat", tags=["Chat"])
 app.include_router(copilot.router, prefix="/api/copilot", tags=["Copilot"])
 app.include_router(credentials.router, prefix="/api/credentials", tags=["Credentials"])
 app.include_router(calendar.router, prefix="/api/calendar", tags=["Calendar"])
+app.include_router(tax.router, prefix="/api/tax", tags=["Tax"])
 
 
 @app.get("/health")

atlas-terminal/server/routers/tax.py

@@ -0,0 +1,113 @@
+"""Tax simulation endpoints.
+
+These endpoints are educational calculators for personal planning.  They are
+not tax advice and intentionally keep assumptions explicit in the payload.
+"""
+
+from __future__ import annotations
+
+from typing import Literal
+
+from fastapi import APIRouter, Query
+
+from server.routers.portfolio import _get_current_quote, _load_positions
+
+router = APIRouter()
+
+UK_CGT_ALLOWANCE_2026 = 3000.0
+UK_CGT_BASIC_RATE = 0.10
+UK_CGT_HIGHER_RATE = 0.20
+
+_FX_TO_GBP = {
+    "GBP": 1.0,
+    "GBX": 0.01,
+    "USD": 0.80,
+    "EUR": 0.86,
+    "DKK": 0.115,
+    "JPY": 0.0053,
+    "KRW": 0.00058,
+    "CHF": 0.90,
+    "CAD": 0.58,
+    "AUD": 0.52,
+}
+
+
+def _fx_to_gbp(currency: str) -> float:
+    return _FX_TO_GBP.get((currency or "USD").upper(), _FX_TO_GBP["USD"])
+
+
+def _position_gain(position: dict) -> dict:
+    ticker = str(position.get("ticker", "")).upper()
+    quantity = float(position.get("quantity") or 0)
+    avg_price = float(position.get("avg_price") or 0)
+    exchange = str(position.get("exchange") or "")
+    quote = _get_current_quote(ticker, exchange)
+    current_price = float(quote.get("price") or avg_price)
+    cost_currency = str(position.get("currency") or position.get("avg_price_currency") or quote.get("currency") or "USD").upper()
+    current_currency = str(quote.get("currency") or cost_currency).upper()
+    cost_gbp = quantity * avg_price * _fx_to_gbp(cost_currency)
+    value_gbp = quantity * current_price * _fx_to_gbp(current_currency)
+    gain_gbp = value_gbp - cost_gbp
+    return {
+        "ticker": ticker,
+        "quantity": quantity,
+        "avg_price": avg_price,
+        "current_price": current_price,
+        "cost_currency": cost_currency,
+        "current_currency": current_currency,
+        "cost_gbp": round(cost_gbp, 2),
+        "value_gbp": round(value_gbp, 2),
+        "gain_gbp": round(gain_gbp, 2),
+        "gain_per_share_gbp": round(gain_gbp / quantity, 4) if quantity else 0,
+    }
+
+
+def _optimal_realization(gains: list[dict], allowance: float) -> list[dict]:
+    remaining = allowance
+    suggestions = []
+    positive = [item for item in gains if item["gain_gbp"] > 0 and item["quantity"] > 0]
+    for item in sorted(positive, key=lambda row: row["gain_gbp"]):
+        if remaining <= 0:
+            break
+        gain_per_share = item["gain_gbp"] / item["quantity"]
+        if gain_per_share <= 0:
+            continue
+        shares = min(item["quantity"], remaining / gain_per_share)
+        realized_gain = min(item["gain_gbp"], shares * gain_per_share)
+        suggestions.append(
+            {
+                "ticker": item["ticker"],
+                "shares_to_sell": round(shares, 6),
+                "estimated_gain_gbp": round(realized_gain, 2),
+            }
+        )
+        remaining -= realized_gain
+    return suggestions
+
+
+@router.get("/uk/cgt/{user_id}", summary="UK CGT allowance simulator")
+async def simulate_uk_cgt(
+    user_id: str,
+    income_band: Literal["basic", "higher"] = Query("higher"),
+):
+    positions = _load_positions()
+    gains = [_position_gain(position) for position in positions if position.get("ticker")]
+    total_gain = round(sum(item["gain_gbp"] for item in gains if item["gain_gbp"] > 0), 2)
+    taxable = round(max(0.0, total_gain - UK_CGT_ALLOWANCE_2026), 2)
+    rate = UK_CGT_HIGHER_RATE if income_band == "higher" else UK_CGT_BASIC_RATE
+    tax = round(taxable * rate, 2)
+    return {
+        "user_id": user_id,
+        "income_band": income_band,
+        "total_unrealized_gain_gbp": total_gain,
+        "allowance": UK_CGT_ALLOWANCE_2026,
+        "allowance_remaining": round(max(0.0, UK_CGT_ALLOWANCE_2026 - total_gain), 2),
+        "taxable_if_sold_all": taxable,
+        "tax_if_sold_all": tax,
+        "rate": rate,
+        "optimal_realization": _optimal_realization(gains, UK_CGT_ALLOWANCE_2026),
+        "positions": gains,
+        "tax_year_end": "2026-04-05",
+        "fx_source": "static_estimate",
+        "disclaimer": "Educational estimate only. Not tax advice. Consult HMRC guidance or a qualified adviser.",
+    }

atlas-terminal/tests/test_smoke.py

@@ -33,6 +33,7 @@ EXPECTED_PREFIXES = [
     "/api/research",
     "/api/screener",
     "/api/technical",
+    "/api/tax",
     "/api/valuation",
 ]
 
@@ -259,3 +260,25 @@ def test_portfolio_correlation_uses_gateway_history(monkeypatch) -> None:
     assert data["available"] is True
     assert data["tickers"] == ["AAA", "BBB"]
     assert data["matrix"][0][0] == 1.0
+
+
+def test_uk_cgt_calculator_uses_portfolio_positions(monkeypatch) -> None:
+    from server.routers import tax
+
+    monkeypatch.setattr(
+        tax,
+        "_load_positions",
+        lambda: [
+            {"ticker": "AAPL", "quantity": 10, "avg_price": 100, "currency": "USD"},
+        ],
+    )
+    monkeypatch.setattr(tax, "_get_current_quote", lambda ticker, exchange="": {"price": 200, "currency": "USD"})
+
+    with TestClient(app) as client:
+        response = client.get("/api/tax/uk/cgt/local?income_band=higher")
+
+    assert response.status_code == 200
+    data = response.json()
+    assert data["total_unrealized_gain_gbp"] == 800.0
+    assert data["tax_if_sold_all"] == 0.0
+    assert data["positions"][0]["ticker"] == "AAPL"