diff --git a/frontend/src/__tests__/history-marketplace-sell-button.test.ts b/frontend/src/__tests__/history-marketplace-sell-button.test.ts
index 6730be160..9870779aa 100644
--- a/frontend/src/__tests__/history-marketplace-sell-button.test.ts
+++ b/frontend/src/__tests__/history-marketplace-sell-button.test.ts
@@ -77,6 +77,7 @@ jest.mock('../state', () => ({
 import * as api from '../api';
 import { getCurrentUser } from '../state';
 import { confirmDialog } from '../confirmDialog';
+import { formatCurrency } from '../utils';
 
 // Administrators group GUID -- mirrors ADMINISTRATORS_GROUP_ID in
 // frontend/src/permissions.ts. Without this, isAdmin() returns false and
@@ -452,6 +453,36 @@ describe('Marketplace consent modal residual proration (issue #808 follow-up)',
     expect(text).not.toContain('$585');
   });
 
+  // Issue #318: list price, AWS fee and net proceeds were each rounded to whole
+  // dollars on their own, so a $142.50 listing showed $143 = $17 + $125. Run
+  // the real formatter and check that the three lines reconcile to the cent.
+  test('issue #318: list price, fee and net proceeds show cents and add up', async () => {
+    const realFormat = jest.requireActual<typeof import('../utils')>('../utils').formatCurrency;
+    (formatCurrency as jest.Mock).mockImplementation(realFormat);
+    try {
+      const PARTWAY = new Date(Date.now() - 2.5 * 30.4375 * 24 * 60 * 60 * 1000).toISOString();
+      (api.getHistory as jest.Mock).mockResolvedValue({
+        summary: {},
+        purchases: [makeRow({
+          purchase_id: 'ri-cents', offering_class: 'standard', term: 1, timestamp: PARTWAY,
+          count: 1, upfront_cost: 200, monthly_cost: 0,
+        })],
+      });
+      await loadHistory();
+      document.querySelector<HTMLButtonElement>('.history-marketplace-sell-btn[data-marketplace-sell-id="ri-cents"]')!.click();
+      await Promise.resolve();
+      await Promise.resolve();
+
+      const arg = (confirmDialog as jest.Mock).mock.calls[0][0] as { body: HTMLElement };
+      const values = Array.from(arg.body.querySelectorAll('dd')).map(dd => dd.textContent);
+      // remaining 9 of 12 months: residual 150, list 142.50, net 142.50 * 0.88 = 125.40.
+      expect(values).toEqual(expect.arrayContaining(['$142.50', '$17.10', '$125.40']));
+      expect(values).not.toContain('$143');
+    } finally {
+      (formatCurrency as jest.Mock).mockImplementation((val) => `$${val || 0}`);
+    }
+  });
+
   test('shows default price as unavailable for a no-upfront RI instead of a fabricated price', async () => {
     const JUST_NOW = new Date(Date.now() - 24 * 60 * 60 * 1000).toISOString();
     (api.getHistory as jest.Mock).mockResolvedValue({
diff --git a/frontend/src/__tests__/history.test.ts b/frontend/src/__tests__/history.test.ts
index f2b8ebf97..564e4ba3e 100644
--- a/frontend/src/__tests__/history.test.ts
+++ b/frontend/src/__tests__/history.test.ts
@@ -33,6 +33,7 @@ jest.mock('../utils', () => ({
     if (!str) return '';
     return str.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;').replace(/"/g, '&quot;').replace(/'/g, '&#39;');
   }),
+  amortizedMonthly: jest.requireActual('../utils').amortizedMonthly,
   populateAccountFilter: jest.fn(() => Promise.resolve())
 }));
 
@@ -105,6 +106,30 @@ describe('History Module', () => {
     expect(queue?.querySelectorAll('td')[8]?.textContent).toBe('--');
   });
 
+  // Issue #318: with amortize on, the upfront is already in Monthly Cost, so
+  // the Upfront cell is muted and labeled to keep it from reading as additive.
+  test.each([false, true])('upfront folded into monthly with amortization %s is labeled only when on', async (amortize) => {
+    (getAmortizeUpfront as jest.Mock).mockReturnValue(amortize);
+    const purchase = {
+      timestamp: '2026-09-29T00:00:00Z', provider: 'aws', service: 'ec2', resource_type: 'm5.large',
+      region: 'us-east-1', count: 1, term: 1, upfront_cost: 1200, monthly_cost: 100, estimated_savings: 300,
+    };
+    (api.getHistory as jest.Mock).mockResolvedValue({ summary: {}, purchases: [
+      { ...purchase, purchase_id: 'complete', status: 'completed' },
+      { ...purchase, purchase_id: 'pending', status: 'pending' },
+    ] });
+    await loadHistory();
+    const historyCells = document.querySelectorAll('#history-list tr[data-execution-id="complete"] td');
+    const queueCells = document.querySelectorAll('#purchases-approval-queue tr[data-execution-id="pending"] td');
+    expect(historyCells[9]?.textContent).toBe(amortize ? '$200' : '$100');
+    expect(queueCells[7]?.textContent).toBe(amortize ? '$200' : '$100');
+    for (const upfront of [historyCells[8], queueCells[8]]) {
+      expect(upfront?.classList.contains('upfront-in-monthly')).toBe(amortize);
+      expect(upfront?.textContent).toBe(amortize ? '$1200(in monthly)' : '$1200');
+      expect(upfront?.getAttribute('title')).toBe(amortize ? 'Included in the amortized monthly cost' : null);
+    }
+  });
+
   describe('initHistoryDateRange', () => {
     test('sets default date range to 7 days', () => {
       initHistoryDateRange();
diff --git a/frontend/src/__tests__/settings.test.ts b/frontend/src/__tests__/settings.test.ts
index 0736b4e97..46d34f3be 100644
--- a/frontend/src/__tests__/settings.test.ts
+++ b/frontend/src/__tests__/settings.test.ts
@@ -1020,6 +1020,31 @@ describe('Settings Module', () => {
         expect(isUnsavedChanges()).toBe(false);
       });
 
+      test.each(['12.7', '-40', '500'])('an SP card coverage of %s aborts the save before any PUT (#318)', async (value) => {
+        await loadWithCoverage50();
+        mockShowToast.mockClear();
+        (document.getElementById('aws-savings-plans-compute-coverage') as HTMLInputElement).value = value;
+
+        await saveGlobalSettings({ preventDefault: jest.fn() } as unknown as Event);
+
+        expect(api.updateConfig).not.toHaveBeenCalled();
+        expect(api.updateServiceConfig).not.toHaveBeenCalled();
+        expect(mockShowToast).toHaveBeenCalledWith(expect.objectContaining({
+          kind: 'error',
+          message: expect.stringContaining('whole number between 0 and 100 (savings-plans-compute)'),
+        }));
+        expect(isUnsavedChanges()).toBe(true);
+      });
+
+      test.each([['0', 0], ['100', 100]])('an SP card coverage of %s is within range and saved (#318)', async (value, sent) => {
+        await loadWithCoverage50();
+        (document.getElementById('aws-savings-plans-compute-coverage') as HTMLInputElement).value = value;
+
+        await saveGlobalSettings({ preventDefault: jest.fn() } as unknown as Event);
+
+        expect(coverageSentFor('savings-plans-compute')).toBe(sent);
+      });
+
       test('a saved service payment edit leaves nothing unsaved (#576)', async () => {
         await loadWithCoverage50();
         (document.getElementById('aws-ec2-payment') as HTMLSelectElement).value = 'partial-upfront';
diff --git a/frontend/src/history.ts b/frontend/src/history.ts
index b4c183d44..5051f8ad3 100644
--- a/frontend/src/history.ts
+++ b/frontend/src/history.ts
@@ -562,6 +562,16 @@ function providerCell(p: HistoryPurchase): string {
   return `<span class="provider-badge ${safeProvider}">${safeProvider.toUpperCase()}</span>`;
 }
 
+// upfrontCell renders the Upfront Cost cell. With amortize on, the upfront is
+// already spread into the Monthly Cost column, so the cell is muted and
+// labeled to stop Upfront + 12 x Monthly being read as additive (#318).
+function upfrontCell(p: HistoryPurchase, amortize: boolean): string {
+  const amount = formatCurrency(p.upfront_cost);
+  const folded = amortize && p.monthly_cost != null && p.upfront_cost != null && p.upfront_cost > 0 && p.term > 0;
+  if (!folded) return `<td>${amount}</td>`;
+  return `<td class="upfront-in-monthly" title="Included in the amortized monthly cost">${amount}<div class="upfront-in-monthly-note">(in monthly)</div></td>`;
+}
+
 // canCancelPendingRow returns true when the current session is permitted
 // to cancel the given pending/notified history row via the session-authed
 // Cancel button (issue #46). UX gate only — the backend
@@ -1215,6 +1225,7 @@ function renderHistoryList(purchases: HistoryPurchase[]): void {
   const colFilters = state.getPurchaseHistoryColumnFilters();
   const visible = applyPurchaseHistoryColumnFilters(statusFiltered, colFilters);
 
+  const amortize = state.getAmortizeUpfront();
   const tableRows = visible.map(p => {
     const statusCell = (() => {
       const badge = statusBadgeHTML(normalizeStatus(p));
@@ -1229,7 +1240,6 @@ function renderHistoryList(purchases: HistoryPurchase[]): void {
     })();
     const execIdAttr = p.purchase_id ? ` data-execution-id="${escapeHtmlAttr(p.purchase_id)}"` : '';
     const planCellContent = renderActionCell(p);
-    const amortize = state.getAmortizeUpfront();
     const rawMonthly = p.monthly_cost != null ? p.monthly_cost : null;
     const displayMonthly = (rawMonthly != null && amortize)
       ? (p.upfront_cost == null ? null : amortizedMonthly(rawMonthly, p.upfront_cost, p.term))
@@ -1247,7 +1257,7 @@ function renderHistoryList(purchases: HistoryPurchase[]): void {
         <td>${escapeHtml(p.region)}</td>
         <td>${p.count}</td>
         <td>${formatTerm(p.term)}</td>
-        <td>${formatCurrency(p.upfront_cost)}</td>
+        ${upfrontCell(p, amortize)}
         <td>${monthlyCostCell}</td>
         <td class="savings">${formatCurrency(p.estimated_savings)}</td>
         <td>${planCellContent}</td>
@@ -1255,7 +1265,6 @@ function renderHistoryList(purchases: HistoryPurchase[]): void {
     `;
   }).join('');
 
-  const amortize = state.getAmortizeUpfront();
   const monthlyColHeader = amortize ? 'Monthly Cost (amortized)' : 'Monthly Cost';
   const fbtn = (col: PurchaseHistoryColumnId): string => renderHistoryFilterButton(
     col, PURCHASE_HISTORY_LABELS[col], colFilters[col] != null,
@@ -1582,11 +1591,17 @@ function wireRowActionHandlers(container: HTMLElement): void {
           addRow('Resource type', purchase.resource_type || '-');
           addRow('Remaining term', remainingMonths === 1 ? '1 month' : `${remainingMonths} months`);
           if (listPricePerUnit > 0) {
+            // Show cents, and derive the fee from the two rounded totals, so
+            // the three lines always reconcile (fee + net = list price). The
+            // dashboard's whole-dollar default rounded each line on its own,
+            // e.g. $101 = $12 + $88 for a $100.50 listing (#318).
+            const listCents = Math.round(listPriceTotal * 100);
+            const netCents = Math.round(netProceedsTotal * 100);
             addRow('Default list price', count > 1
-              ? `${formatCurrency(listPricePerUnit)}/unit (${formatCurrency(listPriceTotal)} total for ${count} units)`
-              : formatCurrency(listPriceTotal));
-            addRow(`AWS fee (${AWS_MARKETPLACE_FEE_PERCENT}%)`, formatCurrency(listPriceTotal * (AWS_MARKETPLACE_FEE_PERCENT / 100)));
-            addRow('Estimated net proceeds', formatCurrency(netProceedsTotal));
+              ? `${formatCurrency(listPricePerUnit, '$', 2)}/unit (${formatCurrency(listCents / 100, '$', 2)} total for ${count} units)`
+              : formatCurrency(listCents / 100, '$', 2));
+            addRow(`AWS fee (${AWS_MARKETPLACE_FEE_PERCENT}%)`, formatCurrency((listCents - netCents) / 100, '$', 2));
+            addRow('Estimated net proceeds', formatCurrency(netCents / 100, '$', 2));
           } else {
             // No default price can be computed (no upfront cost or unknown
             // term) -- listing will be rejected server-side unless a custom
@@ -1837,6 +1852,7 @@ export function renderApprovalQueue(purchases: HistoryPurchase[]): void {
   const colFilters = state.getApprovalQueueColumnFilters();
   const visible = applyApprovalQueueColumnFilters(pending, colFilters);
 
+  const amortize = state.getAmortizeUpfront();
   const rows = visible.map(p => {
     const actions = renderPendingActionButtons(p);
     const actionsCell = actions || '<span class="muted">-</span>';
@@ -1852,7 +1868,6 @@ export function renderApprovalQueue(purchases: HistoryPurchase[]): void {
       : '<span class="muted">-</span>';
     const termCell = p.term ? escapeHtml(formatTerm(p.term)) : '<span class="muted">-</span>';
     const paymentCell = p.payment ? escapeHtml(p.payment) : '<span class="muted">-</span>';
-    const amortize = state.getAmortizeUpfront();
     const rawMonthly = p.monthly_cost != null ? p.monthly_cost : null;
     const displayMonthly = (rawMonthly != null && amortize)
       ? (p.upfront_cost == null ? null : amortizedMonthly(rawMonthly, p.upfront_cost, p.term))
@@ -1871,7 +1886,7 @@ export function renderApprovalQueue(purchases: HistoryPurchase[]): void {
         <td>${termCell}</td>
         <td>${paymentCell}</td>
         <td>${monthlyCostCell}</td>
-        <td>${formatCurrency(p.upfront_cost)}</td>
+        ${upfrontCell(p, amortize)}
         <td class="savings">${formatCurrency(p.estimated_savings)}</td>
         <td>${createdBy}</td>
         <td>${actionsCell}</td>
@@ -1879,7 +1894,6 @@ export function renderApprovalQueue(purchases: HistoryPurchase[]): void {
     `;
   }).join('');
 
-  const amortize = state.getAmortizeUpfront();
   const monthlyColHeader = amortize ? 'Monthly Cost (amortized)' : 'Monthly Cost';
   // monthlyColHeader is a hardcoded constant string (no user data), so
   // interpolating it directly into the template is safe.
diff --git a/frontend/src/settings.ts b/frontend/src/settings.ts
index efbed45af..e0c9c6f3f 100644
--- a/frontend/src/settings.ts
+++ b/frontend/src/settings.ts
@@ -3435,6 +3435,26 @@ async function renderAccountsOverview(): Promise<void> {
   });
 }
 
+/**
+ * Names of the per-Savings-Plan coverage cards whose edited value is not a
+ * whole number between 0 and 100. Untouched cards and empty inputs are not
+ * checked: the save keeps their persisted value, as it always has.
+ */
+function invalidEditedCardCoverages(): string[] {
+  const bad: string[] = [];
+  for (const field of SERVICE_FIELDS) {
+    if (!('coverageId' in field) || !field.coverageId) continue;
+    const input = byId<HTMLInputElement>(field.coverageId);
+    const raw = input?.value ?? '';
+    if (raw.trim() === '' || getFieldValue(field.coverageId) === savedSnapshot[field.coverageId]) continue;
+    const parsed = Number(raw);
+    if (Number.isInteger(parsed) && parsed >= 0 && parsed <= 100) continue;
+    const title = input?.closest('.service-default-card')?.querySelector('h5')?.textContent?.trim();
+    bad.push(title || field.service);
+  }
+  return bad;
+}
+
 /**
  * Save global settings
  */
@@ -3519,6 +3539,17 @@ export async function saveGlobalSettings(e: Event): Promise<void> {
     saveInFlight = false;
     return;
   }
+  // The per-Savings-Plan coverage cards sit outside the settings <form>, so
+  // native min/max validation never runs for them and the inline hint only
+  // paints a message. Apply the global field's whole-number 0..100 rule here,
+  // before any PUT, so a fractional value like 12.7 is not persisted.
+  const badCoverageCards = invalidEditedCardCoverages();
+  if (badCoverageCards.length > 0) {
+    showToast({ message: `Target coverage must be a whole number between 0 and 100 (${badCoverageCards.join(', ')})`, kind: 'error' });
+    if (saveBtn) saveBtn.disabled = false;
+    saveInFlight = false;
+    return;
+  }
 
   const rawOfferingClass = byId<HTMLSelectElement>('setting-ec2-offering-class')?.value ?? 'convertible';
   const offeringClass: 'convertible' | 'standard' = (rawOfferingClass === 'standard') ? 'standard' : 'convertible';
diff --git a/frontend/src/styles/components.css b/frontend/src/styles/components.css
index 5d76ec88e..60a922e45 100644
--- a/frontend/src/styles/components.css
+++ b/frontend/src/styles/components.css
@@ -1440,6 +1440,18 @@ tr.rec-variant-row:hover td:not(.checkbox-col) {
     font-weight: 600;
 }
 
+/* Upfront Cost cell when the amortize toggle folds the upfront into the
+ * Monthly Cost column (#318): muted so the two are not read as additive.
+ */
+.upfront-in-monthly {
+    color: var(--cudly-text-muted);
+}
+
+.upfront-in-monthly-note {
+    font-size: 0.78rem;
+    line-height: 1.25;
+}
+
 /* Purchase detail status badges */
 .status-badge.completed {
     background: var(--cudly-success-bg);
diff --git a/frontend/tests-e2e/amortized-upfront.spec.ts b/frontend/tests-e2e/amortized-upfront.spec.ts
new file mode 100644
index 000000000..4309e7263
--- /dev/null
+++ b/frontend/tests-e2e/amortized-upfront.spec.ts
@@ -0,0 +1,32 @@
+import { test, expect } from '@playwright/test';
+import { mockApi, seedAuth } from './fixtures/recs';
+
+// Issue #318: with amortize on, the upfront is already spread into Monthly
+// Cost, so the Upfront cell is muted and labeled instead of reading as a
+// separate lump sum on top of the amortized monthly figure.
+test('amortize toggle labels the upfront as included in the monthly cost', async ({ page }) => {
+  await seedAuth(page);
+  await mockApi(page);
+  const purchase = {
+    purchase_id: '11111111-1111-1111-1111-111111111111', timestamp: new Date().toISOString(),
+    provider: 'aws', service: 'ec2', resource_type: 'm5.large', region: 'us-east-1',
+    count: 1, term: 1, upfront_cost: 1200, monthly_cost: 100, estimated_savings: 300,
+    offering_class: 'convertible', status: 'completed', account_id: 'account-1',
+  };
+  await page.route('**/api/history**', route => route.fulfill({ json: { summary: {}, purchases: [purchase] } }));
+
+  await page.goto('/purchases/history');
+  const row = page.locator('#history-list tbody tr').first();
+  const upfront = row.locator('td').nth(8);
+  await expect(upfront).toHaveText('$1,200');
+  await expect(upfront).not.toHaveClass(/upfront-in-monthly/);
+
+  await page.locator('#history-amortize-checkbox').check();
+  await expect(row.locator('td').nth(9)).toHaveText('$200');
+  await expect(upfront).toHaveClass(/upfront-in-monthly/);
+  await expect(upfront).toHaveAttribute('title', 'Included in the amortized monthly cost');
+  await expect(upfront).toContainText('(in monthly)');
+
+  await page.locator('#history-amortize-checkbox').uncheck();
+  await expect(upfront).toHaveText('$1,200');
+});