Add HMRC tax reporting to accounts

- Add new HMRC Report tab to accounts reports
- Show total turnover (web + manual sales)
- Calculate cost of goods sold from purchases
- Display gross profit and profit margin
- Show operating expenses breakdown
- Calculate net profit before tax
- Estimate tax liability (19% corporation tax)
- Include HMRC checklist of what needs to be reported
- Help admin prepare for Self Assessment submission

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

src/app/admin/accounts/reports/client.tsx

@@ -8,6 +8,7 @@ interface ReportData {
   orders: Array<{ id: string; total: number; createdAt: Date }>;
   manualSales: Array<{ id: string; total: number; soldAt: Date; createdAt: Date }>;
   expenses: Array<{ id: string; amount: number; date: Date; category: string }>;
+  purchases: Array<{ id: string; total: number; purchasedAt: Date }>;
 }
 
 export default function ReportsPageClient({ data }: { data: ReportData }) {
@@ -29,6 +30,10 @@ export default function ReportsPageClient({ data }: { data: ReportData }) {
       ...e,
       date: typeof e.date === 'string' ? new Date(e.date) : e.date,
     })),
+    purchases: data.purchases.map(p => ({
+      ...p,
+      purchasedAt: typeof p.purchasedAt === 'string' ? new Date(p.purchasedAt) : p.purchasedAt,
+    })),
   };
 
   const monthlyProfit = useMemo(() => {
@@ -98,6 +103,30 @@ export default function ReportsPageClient({ data }: { data: ReportData }) {
       });
   }, [normalizedData]);
 
+  const hmrcReport = useMemo(() => {
+    const totalRevenue = [...normalizedData.orders, ...normalizedData.manualSales].reduce((sum, s: any) => sum + s.total, 0);
+    const costOfGoodsSold = normalizedData.purchases.reduce((sum, p) => sum + p.total, 0);
+    const grossProfit = totalRevenue - costOfGoodsSold;
+    const totalExpenses = normalizedData.expenses.reduce((sum, e) => sum + e.amount, 0);
+    const netProfit = grossProfit - totalExpenses;
+
+    // UK tax estimation: 19% corporation tax for profits (simplified)
+    // Self-employed allowance is £1,000
+    const taxableProfit = Math.max(0, netProfit - 100000); // Simplified threshold
+    const estimatedTax = Math.max(0, Math.round(taxableProfit * 0.19));
+
+    return {
+      totalRevenue,
+      costOfGoodsSold,
+      grossProfit,
+      grossMargin: totalRevenue > 0 ? (grossProfit / totalRevenue * 100) : 0,
+      totalExpenses,
+      netProfit,
+      profitMargin: totalRevenue > 0 ? (netProfit / totalRevenue * 100) : 0,
+      estimatedTax,
+    };
+  }, [normalizedData]);
+
   return (
     <>
       <div className="mt-6 inline-flex border border-line">
@@ -105,6 +134,7 @@ export default function ReportsPageClient({ data }: { data: ReportData }) {
           { id: 'monthly-profit', label: 'Monthly Profit' },
           { id: 'expense-breakdown', label: 'Expenses' },
           { id: 'cash-flow', label: 'Cash Flow' },
+          { id: 'hmrc', label: 'HMRC Report' },
         ].map((t) => (
           <button
             key={t.id}
@@ -195,6 +225,74 @@ export default function ReportsPageClient({ data }: { data: ReportData }) {
             </table>
           </div>
         )}
+
+        {tab === 'hmrc' && (
+          <div className="space-y-6">
+            <div className="border border-splash-blue/40 bg-splash-blue/5 px-4 py-3 text-sm text-splash-blue">
+              ⓘ Summary for HMRC Self Assessment. Keep invoices and receipts as evidence.
+            </div>
+
+            <div className="grid gap-4 sm:grid-cols-2">
+              <div className="border border-line p-4">
+                <p className="tag-label">Total Turnover</p>
+                <p className="mt-2 font-mono text-2xl">
+                  <Price cents={hmrcReport.totalRevenue} />
+                </p>
+              </div>
+              <div className="border border-line p-4">
+                <p className="tag-label">Cost of Goods Sold</p>
+                <p className="mt-2 font-mono text-2xl">
+                  <Price cents={hmrcReport.costOfGoodsSold} />
+                </p>
+              </div>
+              <div className="border border-line p-4">
+                <p className="tag-label">Gross Profit</p>
+                <p className="mt-2 font-mono text-2xl">
+                  <Price cents={hmrcReport.grossProfit} />
+                </p>
+                <p className="mt-1 text-xs text-muted">{hmrcReport.grossMargin.toFixed(1)}% margin</p>
+              </div>
+              <div className="border border-line p-4">
+                <p className="tag-label">Operating Expenses</p>
+                <p className="mt-2 font-mono text-2xl">
+                  <Price cents={hmrcReport.totalExpenses} />
+                </p>
+              </div>
+            </div>
+
+            <div className="border-2 border-line p-6">
+              <div className="flex items-baseline justify-between">
+                <p className="font-display text-lg">Net Profit (before tax)</p>
+                <p className={`font-mono text-3xl font-medium ${hmrcReport.netProfit >= 0 ? 'text-green-600' : 'text-splash-pink'}`}>
+                  <Price cents={hmrcReport.netProfit} />
+                </p>
+              </div>
+              <p className="mt-2 text-xs text-muted">{hmrcReport.profitMargin.toFixed(1)}% of revenue</p>
+            </div>
+
+            <div className="border-2 border-splash-pink p-6">
+              <div className="flex items-baseline justify-between">
+                <p className="font-display text-lg">Estimated Tax Liability</p>
+                <p className="font-mono text-3xl font-medium text-splash-pink">
+                  <Price cents={hmrcReport.estimatedTax} />
+                </p>
+              </div>
+              <p className="mt-3 text-xs text-muted">
+                Based on 19% corporation tax on profits. Self-employed? Your actual rate may differ. Consult an accountant for accurate figures.
+              </p>
+            </div>
+
+            <div className="text-xs text-muted space-y-2">
+              <p><strong>What to report to HMRC:</strong></p>
+              <ul className="list-disc pl-5 space-y-1">
+                <li>Total turnover: <span className="font-mono"><Price cents={hmrcReport.totalRevenue} /></span></li>
+                <li>Cost of sales (purchases): <span className="font-mono"><Price cents={hmrcReport.costOfGoodsSold} /></span></li>
+                <li>Running expenses: <span className="font-mono"><Price cents={hmrcReport.totalExpenses} /></span></li>
+                <li>Profit before tax: <span className="font-mono"><Price cents={hmrcReport.netProfit} /></span></li>
+              </ul>
+            </div>
+          </div>
+        )}
       </div>
     </>
   );