diff --git a/src/lib/invoice-generation.ts b/src/lib/invoice-generation.ts
new file mode 100644
index 0000000..6e5d8fe
--- /dev/null
+++ b/src/lib/invoice-generation.ts
@@ -0,0 +1,157 @@
+import { supabase } from "@/integrations/supabase/client";
+
+export interface GenerateInvoiceArgs {
+  clientId: string;
+  caseIds: string[]; // restrict billing to these cases (must belong to client)
+  createdBy: string;
+  invoicePrefix?: string;
+  taxRate?: number; // e.g. 0.07
+  notes?: string;
+  dueDays?: number;
+}
+
+export interface GenerateInvoiceResult {
+  invoiceId: string;
+  invoiceNumber: string;
+}
+
+export async function generateInvoiceForClient(args: GenerateInvoiceArgs): Promise<GenerateInvoiceResult> {
+  const { clientId, caseIds, createdBy } = args;
+  const taxRate = args.taxRate ?? 0;
+  const dueDays = args.dueDays ?? 30;
+  if (caseIds.length === 0) throw new Error("No cases selected");
+
+  // Pull unbilled time + expenses for the selected cases
+  const [{ data: time, error: te }, { data: exp, error: ee }] = await Promise.all([
+    supabase
+      .from("time_entries")
+      .select("id, case_id, work_date, hours, hourly_rate, description, user_id, billable, invoice_id")
+      .in("case_id", caseIds)
+      .eq("billable", true)
+      .is("invoice_id", null),
+    supabase
+      .from("expenses")
+      .select("id, case_id, expense_date, amount, description, user_id, billable, invoice_id")
+      .in("case_id", caseIds)
+      .eq("billable", true)
+      .is("invoice_id", null),
+  ]);
+  if (te) throw te;
+  if (ee) throw ee;
+
+  if ((time?.length ?? 0) === 0 && (exp?.length ?? 0) === 0) {
+    throw new Error("No unbilled time or expenses on the selected cases");
+  }
+
+  const subtotal =
+    (time ?? []).reduce((s, t) => s + Number(t.hours) * Number(t.hourly_rate), 0) +
+    (exp ?? []).reduce((s, e) => s + Number(e.amount), 0);
+  const tax = +(subtotal * taxRate).toFixed(2);
+  const total = +(subtotal + tax).toFixed(2);
+
+  const yr = new Date().getFullYear();
+  const prefix = args.invoicePrefix?.trim() || "INV";
+  const num = `${prefix}-${yr}-${Math.floor(1000 + Math.random() * 9000)}`;
+  const due = new Date();
+  due.setDate(due.getDate() + dueDays);
+
+  const { data: inv, error: ie } = await supabase
+    .from("invoices")
+    .insert({
+      invoice_number: num,
+      client_id: clientId,
+      case_id: caseIds.length === 1 ? caseIds[0] : null,
+      status: "draft",
+      issue_date: new Date().toISOString().slice(0, 10),
+      due_date: due.toISOString().slice(0, 10),
+      subtotal,
+      tax,
+      total,
+      notes: args.notes ?? null,
+      created_by: createdBy,
+    })
+    .select("id, invoice_number")
+    .single();
+  if (ie || !inv) throw ie ?? new Error("Failed to create invoice");
+
+  // Build line items grouped per case in case order
+  const lineItems: any[] = [];
+  let order = 0;
+  for (const cid of caseIds) {
+    const ts = (time ?? [])
+      .filter((t) => t.case_id === cid)
+      .sort((a, b) => (a.work_date < b.work_date ? -1 : 1));
+    const es = (exp ?? [])
+      .filter((e) => e.case_id === cid)
+      .sort((a, b) => (a.expense_date < b.expense_date ? -1 : 1));
+    for (const t of ts) {
+      const amount = +(Number(t.hours) * Number(t.hourly_rate)).toFixed(2);
+      lineItems.push({
+        invoice_id: inv.id,
+        case_id: cid,
+        kind: "time",
+        description: t.description,
+        work_date: t.work_date,
+        quantity: t.hours,
+        rate: t.hourly_rate,
+        amount,
+        time_entry_id: t.id,
+        user_id: t.user_id,
+        sort_order: order++,
+      });
+    }
+    for (const e of es) {
+      lineItems.push({
+        invoice_id: inv.id,
+        case_id: cid,
+        kind: "expense",
+        description: e.description,
+        work_date: e.expense_date,
+        quantity: 1,
+        rate: e.amount,
+        amount: e.amount,
+        expense_id: e.id,
+        user_id: e.user_id,
+        sort_order: order++,
+      });
+    }
+  }
+  if (lineItems.length) {
+    const { error: lierr } = await supabase.from("invoice_line_items").insert(lineItems);
+    if (lierr) throw lierr;
+  }
+
+  // Mark source records as billed
+  const timeIds = (time ?? []).map((t) => t.id);
+  const expIds = (exp ?? []).map((e) => e.id);
+  if (timeIds.length) await supabase.from("time_entries").update({ invoice_id: inv.id }).in("id", timeIds);
+  if (expIds.length) await supabase.from("expenses").update({ invoice_id: inv.id }).in("id", expIds);
+
+  return { invoiceId: inv.id, invoiceNumber: inv.invoice_number };
+}
+
+export async function recalcInvoiceTotals(invoiceId: string, taxRate?: number) {
+  const { data: items } = await supabase
+    .from("invoice_line_items")
+    .select("amount")
+    .eq("invoice_id", invoiceId);
+  const subtotal = (items ?? []).reduce((s, l: any) => s + Number(l.amount), 0);
+  let tax = 0;
+  if (taxRate != null) {
+    tax = +(subtotal * taxRate).toFixed(2);
+  } else {
+    // Preserve existing tax ratio if present
+    const { data: inv } = await supabase
+      .from("invoices")
+      .select("subtotal, tax")
+      .eq("id", invoiceId)
+      .maybeSingle();
+    if (inv && Number(inv.subtotal) > 0) {
+      const ratio = Number(inv.tax) / Number(inv.subtotal);
+      tax = +(subtotal * ratio).toFixed(2);
+    }
+  }
+  const total = +(subtotal + tax).toFixed(2);
+  await supabase.from("invoices").update({ subtotal, tax, total }).eq("id", invoiceId);
+  return { subtotal, tax, total };
+}
diff --git a/src/lib/invoice-pdf.ts b/src/lib/invoice-pdf.ts
new file mode 100644
index 0000000..0e22872
--- /dev/null
+++ b/src/lib/invoice-pdf.ts
@@ -0,0 +1,334 @@
+import jsPDF from "jspdf";
+import { formatDate } from "./format";
+
+const PAGE_W = 612;
+const PAGE_H = 792;
+const MARGIN = 54;
+const CONTENT_W = PAGE_W - MARGIN * 2;
+
+export interface InvoiceLineItem {
+  kind: string;
+  description: string;
+  work_date: string | null;
+  quantity: number;
+  rate: number;
+  amount: number;
+  user_name?: string | null;
+}
+
+export interface InvoiceCaseGroup {
+  caseNumber: string;
+  caseTitle: string;
+  practiceArea?: string | null;
+  items: InvoiceLineItem[];
+  subtotal: number;
+}
+
+export interface InvoicePdfInput {
+  firm: {
+    name?: string | null;
+    address1?: string | null;
+    address2?: string | null;
+    city?: string | null;
+    state?: string | null;
+    postal?: string | null;
+    email?: string | null;
+    phone?: string | null;
+    website?: string | null;
+    footerNote?: string | null;
+    logoDataUrl?: string | null;
+  };
+  client: {
+    name: string;
+    contact?: string | null;
+    address1?: string | null;
+    address2?: string | null;
+    city?: string | null;
+    state?: string | null;
+    postal?: string | null;
+  };
+  invoice: {
+    number: string;
+    issueDate: string;
+    dueDate?: string | null;
+    status: string;
+    notes?: string | null;
+  };
+  groups: InvoiceCaseGroup[];
+  totals: {
+    subtotal: number;
+    tax: number;
+    total: number;
+    paid: number;
+    balance: number;
+  };
+}
+
+const fmtCurrency = (n: number) =>
+  new Intl.NumberFormat("en-US", { style: "currency", currency: "USD" }).format(n || 0);
+
+function setFont(pdf: jsPDF, opts: { bold?: boolean; italic?: boolean; size?: number; color?: [number, number, number] }) {
+  let style: "normal" | "bold" | "italic" | "bolditalic" = "normal";
+  if (opts.bold && opts.italic) style = "bolditalic";
+  else if (opts.bold) style = "bold";
+  else if (opts.italic) style = "italic";
+  pdf.setFont("helvetica", style);
+  pdf.setFontSize(opts.size ?? 10);
+  if (opts.color) pdf.setTextColor(...opts.color);
+  else pdf.setTextColor(20, 24, 32);
+}
+
+function wrap(pdf: jsPDF, text: string, maxWidth: number): string[] {
+  if (!text) return [""];
+  return pdf.splitTextToSize(text, maxWidth) as string[];
+}
+
+export async function downloadInvoicePdf(input: InvoicePdfInput, filename: string) {
+  const pdf = new jsPDF({ unit: "pt", format: "letter" });
+  const accent: [number, number, number] = [30, 58, 95]; // deep navy
+  const muted: [number, number, number] = [110, 116, 128];
+  const rule: [number, number, number] = [220, 224, 232];
+
+  let y = MARGIN;
+  const ensure = (need: number) => {
+    if (y + need > PAGE_H - MARGIN - 40) {
+      drawPageFooter(pdf, input);
+      pdf.addPage();
+      y = MARGIN;
+    }
+  };
+
+  // ===== Header band =====
+  // Firm name + address (left)
+  if (input.firm.logoDataUrl) {
+    try {
+      pdf.addImage(input.firm.logoDataUrl, "PNG", MARGIN, y, 110, 44, undefined, "FAST");
+    } catch {
+      // ignore
+    }
+  }
+  const headerLeftX = input.firm.logoDataUrl ? MARGIN + 122 : MARGIN;
+  setFont(pdf, { bold: true, size: 14, color: accent });
+  pdf.text(input.firm.name || "Firm", headerLeftX, y + 14);
+  setFont(pdf, { size: 9, color: muted });
+  let fy = y + 28;
+  const firmLines = [
+    input.firm.address1,
+    input.firm.address2,
+    [input.firm.city, input.firm.state, input.firm.postal].filter(Boolean).join(", "),
+    [input.firm.phone, input.firm.email].filter(Boolean).join("  ·  "),
+    input.firm.website,
+  ].filter((l): l is string => !!l && l.trim().length > 0);
+  for (const l of firmLines) {
+    pdf.text(l, headerLeftX, fy);
+    fy += 11;
+  }
+
+  // INVOICE block (right)
+  setFont(pdf, { bold: true, size: 22, color: accent });
+  const titleW = pdf.getTextWidth("INVOICE");
+  pdf.text("INVOICE", PAGE_W - MARGIN - titleW, y + 18);
+  setFont(pdf, { size: 9, color: muted });
+  const labelX = PAGE_W - MARGIN - 150;
+  const valueX = PAGE_W - MARGIN;
+  let iy = y + 36;
+  const drawKV = (k: string, v: string) => {
+    setFont(pdf, { size: 9, color: muted });
+    pdf.text(k, labelX, iy);
+    setFont(pdf, { size: 10, bold: true });
+    const w = pdf.getTextWidth(v);
+    pdf.text(v, valueX - w, iy);
+    iy += 13;
+  };
+  drawKV("Invoice #", input.invoice.number);
+  drawKV("Issue date", formatDate(input.invoice.issueDate));
+  if (input.invoice.dueDate) drawKV("Due date", formatDate(input.invoice.dueDate));
+  drawKV("Status", input.invoice.status.toUpperCase());
+
+  y = Math.max(fy, iy) + 12;
+
+  // Accent rule
+  pdf.setDrawColor(...accent);
+  pdf.setLineWidth(1.2);
+  pdf.line(MARGIN, y, PAGE_W - MARGIN, y);
+  y += 18;
+
+  // ===== Bill To =====
+  setFont(pdf, { size: 8, color: muted });
+  pdf.text("BILL TO", MARGIN, y);
+  setFont(pdf, { bold: true, size: 12, color: accent });
+  pdf.text(input.client.name, MARGIN, y + 14);
+  setFont(pdf, { size: 9, color: muted });
+  let by = y + 28;
+  const clientLines = [
+    input.client.contact,
+    input.client.address1,
+    input.client.address2,
+    [input.client.city, input.client.state, input.client.postal].filter(Boolean).join(", "),
+  ].filter((l): l is string => !!l && l.trim().length > 0);
+  for (const l of clientLines) {
+    pdf.text(l, MARGIN, by);
+    by += 11;
+  }
+  y = by + 16;
+
+  // ===== Column headers =====
+  const colDateX = MARGIN;
+  const colDescX = MARGIN + 64;
+  const colQtyX = MARGIN + 358;
+  const colRateX = MARGIN + 418;
+  const colAmtX = PAGE_W - MARGIN; // right aligned
+  const drawColHeaders = () => {
+    pdf.setFillColor(245, 247, 250);
+    pdf.rect(MARGIN, y - 10, CONTENT_W, 18, "F");
+    setFont(pdf, { bold: true, size: 8, color: accent });
+    pdf.text("DATE", colDateX + 2, y + 2);
+    pdf.text("DESCRIPTION", colDescX, y + 2);
+    pdf.text("QTY/HRS", colQtyX, y + 2);
+    pdf.text("RATE", colRateX, y + 2);
+    const w = pdf.getTextWidth("AMOUNT");
+    pdf.text("AMOUNT", colAmtX - w, y + 2);
+    y += 16;
+  };
+
+  // ===== Per-case groups =====
+  for (const group of input.groups) {
+    ensure(60);
+    // Case header bar
+    pdf.setFillColor(...accent);
+    pdf.rect(MARGIN, y - 10, CONTENT_W, 22, "F");
+    setFont(pdf, { bold: true, size: 11, color: [255, 255, 255] });
+    pdf.text(group.caseTitle, MARGIN + 8, y + 4);
+    const caseMeta = [group.caseNumber, group.practiceArea].filter(Boolean).join("  ·  ");
+    if (caseMeta) {
+      setFont(pdf, { size: 9, color: [220, 228, 240] });
+      const w = pdf.getTextWidth(caseMeta);
+      pdf.text(caseMeta, PAGE_W - MARGIN - 8 - w, y + 4);
+    }
+    y += 22;
+
+    drawColHeaders();
+
+    setFont(pdf, { size: 9, color: [30, 34, 44] });
+    for (const item of group.items) {
+      const descMaxW = colQtyX - colDescX - 8;
+      const descLines = wrap(pdf, item.description || (item.kind === "expense" ? "Expense" : ""), descMaxW);
+      const subLine = item.kind === "time" && item.user_name ? item.user_name : item.kind === "expense" ? "Expense" : "";
+      const lineHeight = 12;
+      const blockH = Math.max(lineHeight * descLines.length + (subLine ? 10 : 0), 16);
+      ensure(blockH + 4);
+
+      // Date
+      setFont(pdf, { size: 9, color: muted });
+      pdf.text(item.work_date ? formatDate(item.work_date) : "—", colDateX + 2, y);
+
+      // Description
+      setFont(pdf, { size: 9, color: [30, 34, 44] });
+      let dy = y;
+      for (const dl of descLines) {
+        pdf.text(dl, colDescX, dy);
+        dy += lineHeight;
+      }
+      if (subLine) {
+        setFont(pdf, { size: 8, color: muted, italic: true });
+        pdf.text(subLine, colDescX, dy);
+      }
+
+      // Qty
+      setFont(pdf, { size: 9, color: [30, 34, 44] });
+      const qtyText = item.kind === "time" ? Number(item.quantity).toFixed(2) : "1";
+      pdf.text(qtyText, colQtyX, y);
+
+      // Rate
+      pdf.text(fmtCurrency(item.rate), colRateX, y);
+
+      // Amount
+      const amt = fmtCurrency(item.amount);
+      const aw = pdf.getTextWidth(amt);
+      pdf.text(amt, colAmtX - aw, y);
+
+      y += blockH + 4;
+      pdf.setDrawColor(...rule);
+      pdf.setLineWidth(0.4);
+      pdf.line(MARGIN, y - 2, PAGE_W - MARGIN, y - 2);
+    }
+
+    // Case subtotal
+    ensure(20);
+    setFont(pdf, { bold: true, size: 9.5, color: accent });
+    const labelTxt = `${group.caseNumber} subtotal`;
+    pdf.text(labelTxt, colRateX - 40, y + 6);
+    const subText = fmtCurrency(group.subtotal);
+    const sw = pdf.getTextWidth(subText);
+    pdf.text(subText, colAmtX - sw, y + 6);
+    y += 22;
+  }
+
+  // ===== Totals =====
+  ensure(110);
+  y += 8;
+  pdf.setDrawColor(...accent);
+  pdf.setLineWidth(1);
+  pdf.line(PAGE_W - MARGIN - 240, y, PAGE_W - MARGIN, y);
+  y += 14;
+
+  const drawTotalRow = (label: string, value: string, opts?: { bold?: boolean; size?: number; color?: [number, number, number] }) => {
+    setFont(pdf, { size: opts?.size ?? 10, bold: opts?.bold, color: opts?.color ?? [30, 34, 44] });
+    pdf.text(label, PAGE_W - MARGIN - 240, y);
+    const w = pdf.getTextWidth(value);
+    pdf.text(value, PAGE_W - MARGIN - w, y);
+    y += 16;
+  };
+
+  drawTotalRow("Subtotal", fmtCurrency(input.totals.subtotal));
+  if (input.totals.tax > 0) drawTotalRow("Tax", fmtCurrency(input.totals.tax));
+  drawTotalRow("Total", fmtCurrency(input.totals.total), { bold: true, size: 11, color: accent });
+  if (input.totals.paid > 0) {
+    drawTotalRow("Amount paid", `- ${fmtCurrency(input.totals.paid)}`, { color: muted });
+    pdf.setDrawColor(...accent);
+    pdf.setLineWidth(0.6);
+    pdf.line(PAGE_W - MARGIN - 240, y - 8, PAGE_W - MARGIN, y - 8);
+    drawTotalRow("Balance due", fmtCurrency(input.totals.balance), { bold: true, size: 12, color: accent });
+  }
+
+  // ===== Notes =====
+  if (input.invoice.notes) {
+    ensure(40);
+    y += 10;
+    setFont(pdf, { bold: true, size: 9, color: accent });
+    pdf.text("NOTES", MARGIN, y);
+    y += 12;
+    setFont(pdf, { size: 9, color: [40, 44, 54] });
+    const lines = wrap(pdf, input.invoice.notes, CONTENT_W);
+    for (const l of lines) {
+      ensure(12);
+      pdf.text(l, MARGIN, y);
+      y += 12;
+    }
+  }
+
+  // Footer on every page
+  drawPageFooter(pdf, input);
+  const total = pdf.getNumberOfPages();
+  for (let i = 1; i <= total; i++) {
+    pdf.setPage(i);
+    setFont(pdf, { size: 8, color: muted });
+    const pageTxt = `Page ${i} of ${total}`;
+    const w = pdf.getTextWidth(pageTxt);
+    pdf.text(pageTxt, PAGE_W - MARGIN - w, PAGE_H - 22);
+  }
+
+  pdf.save(filename.endsWith(".pdf") ? filename : `${filename}.pdf`);
+}
+
+function drawPageFooter(pdf: jsPDF, input: InvoicePdfInput) {
+  const muted: [number, number, number] = [110, 116, 128];
+  pdf.setDrawColor(220, 224, 232);
+  pdf.setLineWidth(0.5);
+  pdf.line(MARGIN, PAGE_H - 36, PAGE_W - MARGIN, PAGE_H - 36);
+  pdf.setFont("helvetica", "italic");
+  pdf.setFontSize(8);
+  pdf.setTextColor(...muted);
+  const note = input.firm.footerNote || `Thank you for your business. Please remit payment to ${input.firm.name || "us"}.`;
+  pdf.text(note, MARGIN, PAGE_H - 22);
+}