diff --git a/src/components/cases/bulk-convert-to-collections-dialog.tsx b/src/components/cases/bulk-convert-to-collections-dialog.tsx
index f1a89d6..242acc4 100644
--- a/src/components/cases/bulk-convert-to-collections-dialog.tsx
+++ b/src/components/cases/bulk-convert-to-collections-dialog.tsx
@@ -72,6 +72,9 @@ export function BulkConvertToCollectionsDialog({ open, onOpenChange, cases, onCr
   const [selected, setSelected] = useState<Set<string>>(new Set());
   const [includeEmpty, setIncludeEmpty] = useState(false);
   const [emptyName, setEmptyName] = useState("");
+  // When true (default), create ONE combined collection per case using the
+  // first selected contact on that case as the primary homeowner.
+  const [combine, setCombine] = useState(true);
 
   const { eligibleCases, skippedCases, clientId } = useMemo(() => {
     const counts = new Map<string, number>();
@@ -95,6 +98,7 @@ export function BulkConvertToCollectionsDialog({ open, onOpenChange, cases, onCr
     setSearch("");
     setIncludeEmpty(false);
     setEmptyName("");
+    setCombine(true);
     if (eligibleCases.length === 0) {
       setContactRows([]);
       return;
@@ -245,16 +249,47 @@ export function BulkConvertToCollectionsDialog({ open, onOpenChange, cases, onCr
       }
 
       const rows: any[] = [];
-      for (const r of selectedRows) {
-        const homeownerId = contactToHomeowner.get(r.contact_id);
-        if (!homeownerId) continue;
-        if (existingPairs.has(`${r.case_id}::${homeownerId}`)) continue;
-        rows.push({
-          case_id: r.case_id,
-          homeowner_id: homeownerId,
-          status: "none",
-          created_by: user?.id,
-        });
+      // Cases that already have ANY collection — skip in combine mode to avoid duplicates.
+      const casesWithExisting = new Set<string>();
+      for (const e of (existing ?? []) as any[]) casesWithExisting.add(e.case_id);
+
+      if (combine) {
+        // Group selected contacts by case, pick first as primary, attach others by name.
+        const byCase = new Map<string, typeof selectedRows>();
+        for (const r of selectedRows) {
+          if (!byCase.has(r.case_id)) byCase.set(r.case_id, [] as any);
+          byCase.get(r.case_id)!.push(r);
+        }
+        for (const [caseId, group] of byCase) {
+          if (casesWithExisting.has(caseId)) continue;
+          const primary = group[0];
+          const primaryHoId = contactToHomeowner.get(primary.contact_id);
+          if (!primaryHoId) continue;
+          const others = group.slice(1).map((r) => r.name);
+          const name =
+            others.length > 0
+              ? `${primary.name} + ${others.length} other${others.length === 1 ? "" : "s"}`
+              : null;
+          rows.push({
+            case_id: caseId,
+            homeowner_id: primaryHoId,
+            status: "none",
+            name,
+            created_by: user?.id,
+          });
+        }
+      } else {
+        for (const r of selectedRows) {
+          const homeownerId = contactToHomeowner.get(r.contact_id);
+          if (!homeownerId) continue;
+          if (existingPairs.has(`${r.case_id}::${homeownerId}`)) continue;
+          rows.push({
+            case_id: r.case_id,
+            homeowner_id: homeownerId,
+            status: "none",
+            created_by: user?.id,
+          });
+        }
       }
 
       if (includeEmpty) {
@@ -410,6 +445,21 @@ export function BulkConvertToCollectionsDialog({ open, onOpenChange, cases, onCr
                 )}
               </div>
 
+              <div className="border rounded-md p-3 space-y-2 bg-muted/20">
+                <label className="flex items-center gap-2 text-sm cursor-pointer">
+                  <Checkbox
+                    checked={combine}
+                    onCheckedChange={(v) => setCombine(!!v)}
+                  />
+                  <span>
+                    Combine homeowners into one collection per case (recommended)
+                    <span className="block text-xs text-muted-foreground font-normal">
+                      First selected contact on each case becomes the primary homeowner. Cases that already have a collection are skipped.
+                    </span>
+                  </span>
+                </label>
+              </div>
+
               <div className="border rounded-md p-3 space-y-2 bg-muted/20">
                 <label className="flex items-center gap-2 text-sm cursor-pointer">
                   <Checkbox
@@ -446,7 +496,9 @@ export function BulkConvertToCollectionsDialog({ open, onOpenChange, cases, onCr
             }
           >
             {submitting && <Loader2 className="h-4 w-4 mr-2 animate-spin" />}
-            Create up to {projectedCount} collection{projectedCount === 1 ? "" : "s"}
+            {combine
+              ? `Create up to ${eligibleCases.length + (includeEmpty ? eligibleCases.length : 0)} collection${eligibleCases.length + (includeEmpty ? eligibleCases.length : 0) === 1 ? "" : "s"}`
+              : `Create up to ${projectedCount} collection${projectedCount === 1 ? "" : "s"}`}
           </Button>
         </DialogFooter>
       </DialogContent>
diff --git a/src/components/cases/collections-tab.tsx b/src/components/cases/collections-tab.tsx
index 8e673da..1e7904d 100644
--- a/src/components/cases/collections-tab.tsx
+++ b/src/components/cases/collections-tab.tsx
@@ -76,6 +76,7 @@ import {
 } from "@dnd-kit/sortable";
 import { SortableLedgerRow } from "./ledger-row";
 import { ApplyCollectionWorkflowDialog } from "@/components/collections/apply-collection-workflow-dialog";
+import { MergeCollectionsDialog } from "./merge-collections-dialog";
 
 const TXN_TYPES = [
   { value: "assessment", label: "Assessment" },
@@ -148,6 +149,7 @@ export function CaseCollectionsTab({
   // dialogs
   const [addOpen, setAddOpen] = useState(false);
   const [newHomeownerOpen, setNewHomeownerOpen] = useState(false);
+  const [mergeOpen, setMergeOpen] = useState(false);
   const [wfCollectionId, setWfCollectionId] = useState<string | null>(null);
 
   const load = async () => {
@@ -258,6 +260,11 @@ export function CaseCollectionsTab({
           <Button variant="outline" onClick={() => setNewHomeownerOpen(true)}>
             <UserPlus className="h-4 w-4 mr-2" /> New homeowner
           </Button>
+          {collections.length >= 2 && (
+            <Button variant="outline" onClick={() => setMergeOpen(true)}>
+              <GitFork className="h-4 w-4 mr-2 rotate-180" /> Merge
+            </Button>
+          )}
           <Button onClick={() => setAddOpen(true)}>
             <Plus className="h-4 w-4 mr-2" /> Add collection
           </Button>
@@ -363,6 +370,14 @@ export function CaseCollectionsTab({
         onCreated={load}
       />
 
+      <MergeCollectionsDialog
+        open={mergeOpen}
+        onOpenChange={setMergeOpen}
+        caseId={caseId}
+        collections={collections as any}
+        onMerged={load}
+      />
+
       <NewHomeownerDialog
         open={newHomeownerOpen}
         onOpenChange={setNewHomeownerOpen}
diff --git a/src/components/cases/convert-to-collections-dialog.tsx b/src/components/cases/convert-to-collections-dialog.tsx
index 4ddfdd8..30cefd7 100644
--- a/src/components/cases/convert-to-collections-dialog.tsx
+++ b/src/components/cases/convert-to-collections-dialog.tsx
@@ -87,6 +87,11 @@ export function ConvertToCollectionsDialog({
   const [status, setStatus] = useState("none");
   const [includeEmpty, setIncludeEmpty] = useState(false);
   const [emptyName, setEmptyName] = useState("");
+  // When true (default), create ONE combined collection for the case using
+  // the first selected contact as the primary homeowner. When false, fall
+  // back to one collection per selected contact.
+  const [combine, setCombine] = useState(true);
+  const [primaryId, setPrimaryId] = useState<string | null>(null);
 
   useEffect(() => {
     if (!open) return;
@@ -95,6 +100,8 @@ export function ConvertToCollectionsDialog({
     setStatus("none");
     setIncludeEmpty(false);
     setEmptyName("");
+    setCombine(true);
+    setPrimaryId(null);
     (async () => {
       setLoading(true);
       const { data: ccs, error } = await supabase
@@ -174,9 +181,10 @@ export function ConvertToCollectionsDialog({
     }
     setSubmitting(true);
     try {
-      // Resolve each selected contact to a homeowner row (find by name on this client, else create).
       const selectedContacts = contacts.filter((c) => selected.has(c.id));
 
+      // Resolve each selected contact to a homeowner row (find by name on
+      // this client, else create). Returns the homeowner_id, in input order.
       let existingHomeowners: any[] = [];
       if (clientId && selectedContacts.length > 0) {
         const { data: hos } = await supabase
@@ -186,7 +194,7 @@ export function ConvertToCollectionsDialog({
         existingHomeowners = hos ?? [];
       }
 
-      const homeownerIds: string[] = [];
+      const homeownerIdByContact = new Map<string, string>();
       for (const c of selectedContacts) {
         const { first, last } = splitName(c.name);
         const match = existingHomeowners.find(
@@ -195,7 +203,7 @@ export function ConvertToCollectionsDialog({
             (h.last_name || "").toLowerCase().trim() === last.toLowerCase(),
         );
         if (match) {
-          homeownerIds.push(match.id);
+          homeownerIdByContact.set(c.id, match.id);
           continue;
         }
         if (!clientId) {
@@ -221,28 +229,67 @@ export function ConvertToCollectionsDialog({
           setSubmitting(false);
           return;
         }
-        homeownerIds.push(newHo.id);
+        homeownerIdByContact.set(c.id, newHo.id);
       }
 
-      // Skip homeowners that already have a collection on this case
       const { data: existingCols } = await supabase
         .from("collections")
         .select("homeowner_id")
         .eq("case_id", caseId);
-      const existingSet = new Set(
+      const existingHomeownerSet = new Set(
         (existingCols ?? [])
           .map((r: any) => r.homeowner_id)
           .filter((id: string | null): id is string => !!id),
       );
+      const hasAnyCollection = (existingCols ?? []).length > 0;
 
-      const rows: any[] = homeownerIds
-        .filter((id) => !existingSet.has(id))
-        .map((homeowner_id) => ({
+      const rows: any[] = [];
+
+      if (combine && selectedContacts.length > 0) {
+        // ONE combined collection for the case. Use the user-picked primary,
+        // or the first selected contact, as homeowner_id.
+        const primaryContact =
+          selectedContacts.find((c) => c.id === primaryId) ?? selectedContacts[0];
+        const primaryHomeownerId = homeownerIdByContact.get(primaryContact.id);
+        if (!primaryHomeownerId) {
+          toast.error("Could not resolve a primary homeowner");
+          setSubmitting(false);
+          return;
+        }
+        if (hasAnyCollection) {
+          toast.info(
+            "This case already has a collection. Use Merge on the Collections tab to combine them.",
+          );
+          setSubmitting(false);
+          return;
+        }
+        const otherNames = selectedContacts
+          .filter((c) => c.id !== primaryContact.id)
+          .map((c) => c.name);
+        const combinedName =
+          otherNames.length > 0
+            ? `${primaryContact.name} + ${otherNames.length} other${otherNames.length === 1 ? "" : "s"}`
+            : null;
+        rows.push({
           case_id: caseId,
-          homeowner_id,
+          homeowner_id: primaryHomeownerId,
           status,
+          name: combinedName,
           created_by: user?.id,
-        }));
+        });
+      } else if (selectedContacts.length > 0) {
+        // Per-homeowner mode (legacy)
+        for (const c of selectedContacts) {
+          const homeowner_id = homeownerIdByContact.get(c.id)!;
+          if (existingHomeownerSet.has(homeowner_id)) continue;
+          rows.push({
+            case_id: caseId,
+            homeowner_id,
+            status,
+            created_by: user?.id,
+          });
+        }
+      }
 
       if (includeEmpty) {
         rows.push({
@@ -287,7 +334,9 @@ export function ConvertToCollectionsDialog({
             <Users className="h-4 w-4" /> Convert case to collections
           </DialogTitle>
           <DialogDescription>
-            Select case contacts tagged as homeowner or tenant to create a collection ledger for each.
+            Select case contacts tagged as homeowner or tenant. By default
+            one combined collection is created for the case using the first
+            selected contact as the primary homeowner.
           </DialogDescription>
         </DialogHeader>
 
@@ -380,6 +429,43 @@ export function ConvertToCollectionsDialog({
             )}
           </div>
 
+          <div className="border rounded-md p-3 space-y-2 bg-muted/20">
+            <label className="flex items-center gap-2 text-sm cursor-pointer">
+              <Checkbox
+                checked={combine}
+                onCheckedChange={(v) => setCombine(!!v)}
+              />
+              <span>
+                Combine into one collection (recommended)
+                <span className="block text-xs text-muted-foreground font-normal">
+                  Creates a single ledger for the case. Uncheck to make one ledger per homeowner.
+                </span>
+              </span>
+            </label>
+            {combine && selected.size > 1 && (
+              <div className="pt-1">
+                <Label className="text-xs">Primary homeowner</Label>
+                <Select
+                  value={primaryId ?? Array.from(selected)[0] ?? ""}
+                  onValueChange={(v) => setPrimaryId(v)}
+                >
+                  <SelectTrigger>
+                    <SelectValue placeholder="Pick primary homeowner" />
+                  </SelectTrigger>
+                  <SelectContent>
+                    {contacts
+                      .filter((c) => selected.has(c.id))
+                      .map((c) => (
+                        <SelectItem key={c.id} value={c.id}>
+                          {c.name}
+                        </SelectItem>
+                      ))}
+                  </SelectContent>
+                </Select>
+              </div>
+            )}
+          </div>
+
           <div className="border rounded-md p-3 space-y-2 bg-muted/20">
             <label className="flex items-center gap-2 text-sm cursor-pointer">
               <Checkbox
@@ -407,8 +493,9 @@ export function ConvertToCollectionsDialog({
             disabled={submitting || (selected.size === 0 && !includeEmpty)}
           >
             {submitting && <Loader2 className="h-4 w-4 mr-2 animate-spin" />}
-            Create {selected.size + (includeEmpty ? 1 : 0)} collection
-            {selected.size + (includeEmpty ? 1 : 0) === 1 ? "" : "s"}
+            {combine && selected.size > 0
+              ? `Create 1 combined collection${includeEmpty ? " + 1 empty" : ""}`
+              : `Create ${selected.size + (includeEmpty ? 1 : 0)} collection${selected.size + (includeEmpty ? 1 : 0) === 1 ? "" : "s"}`}
           </Button>
         </DialogFooter>
       </DialogContent>
diff --git a/src/components/cases/merge-collections-dialog.tsx b/src/components/cases/merge-collections-dialog.tsx
new file mode 100644
index 0000000..d8a7651
--- /dev/null
+++ b/src/components/cases/merge-collections-dialog.tsx
@@ -0,0 +1,251 @@
+import { useEffect, useMemo, useState } from "react";
+import {
+  Dialog,
+  DialogContent,
+  DialogDescription,
+  DialogFooter,
+  DialogHeader,
+  DialogTitle,
+} from "@/components/ui/dialog";
+import { Button } from "@/components/ui/button";
+import { Label } from "@/components/ui/label";
+import { Checkbox } from "@/components/ui/checkbox";
+import {
+  Select,
+  SelectContent,
+  SelectItem,
+  SelectTrigger,
+  SelectValue,
+} from "@/components/ui/select";
+import { Badge } from "@/components/ui/badge";
+import { Alert, AlertDescription } from "@/components/ui/alert";
+import { supabase } from "@/integrations/supabase/client";
+import { Loader2, Merge, AlertTriangle } from "lucide-react";
+import { toast } from "sonner";
+
+interface CollectionRow {
+  id: string;
+  status: string;
+  name: string | null;
+  homeowner_id: string | null;
+  homeowner?: { first_name?: string | null; last_name?: string | null; unit_number?: string | null } | null;
+}
+
+export function MergeCollectionsDialog({
+  open,
+  onOpenChange,
+  caseId,
+  collections,
+  onMerged,
+}: {
+  open: boolean;
+  onOpenChange: (v: boolean) => void;
+  caseId: string;
+  collections: CollectionRow[];
+  onMerged?: () => void;
+}) {
+  const [keepId, setKeepId] = useState<string>("");
+  const [mergeIds, setMergeIds] = useState<Set<string>>(new Set());
+  const [submitting, setSubmitting] = useState(false);
+  const [counts, setCounts] = useState<Record<string, { entries: number; tasks: number }>>({});
+  const [loadingCounts, setLoadingCounts] = useState(false);
+
+  useEffect(() => {
+    if (!open) return;
+    setKeepId(collections[0]?.id ?? "");
+    setMergeIds(new Set());
+    setCounts({});
+    if (collections.length === 0) return;
+    (async () => {
+      setLoadingCounts(true);
+      const ids = collections.map((c) => c.id);
+      const [{ data: entries }, { data: tasks }] = await Promise.all([
+        supabase.from("collection_ledger_entries").select("collection_id").in("collection_id", ids),
+        supabase.from("collection_tasks").select("collection_id").in("collection_id", ids),
+      ]);
+      const next: Record<string, { entries: number; tasks: number }> = {};
+      for (const id of ids) next[id] = { entries: 0, tasks: 0 };
+      for (const e of (entries ?? []) as any[]) next[e.collection_id].entries++;
+      for (const t of (tasks ?? []) as any[]) next[t.collection_id].tasks++;
+      setCounts(next);
+      setLoadingCounts(false);
+    })();
+  }, [open, collections]);
+
+  const labelOf = (c: CollectionRow) =>
+    c.name?.trim() ||
+    (c.homeowner
+      ? `${c.homeowner.last_name ?? ""}, ${c.homeowner.first_name ?? ""}`.replace(/^,\s*/, "")
+      : "Unassigned");
+
+  const sources = useMemo(
+    () => collections.filter((c) => c.id !== keepId),
+    [collections, keepId],
+  );
+
+  const toggleSource = (id: string) =>
+    setMergeIds((prev) => {
+      const next = new Set(prev);
+      if (next.has(id)) next.delete(id);
+      else next.add(id);
+      return next;
+    });
+
+  const submit = async () => {
+    if (!keepId) {
+      toast.error("Pick a collection to keep");
+      return;
+    }
+    if (mergeIds.size === 0) {
+      toast.error("Select at least one collection to merge in");
+      return;
+    }
+    setSubmitting(true);
+    try {
+      const sourceIds = Array.from(mergeIds);
+
+      const { error: e1 } = await supabase
+        .from("collection_ledger_entries")
+        .update({ collection_id: keepId })
+        .in("collection_id", sourceIds);
+      if (e1) throw e1;
+
+      const { error: e2 } = await supabase
+        .from("collection_payment_allocations")
+        .update({ collection_id: keepId })
+        .in("collection_id", sourceIds);
+      if (e2) throw e2;
+
+      const { error: e3 } = await supabase
+        .from("collection_tasks")
+        .update({ collection_id: keepId })
+        .in("collection_id", sourceIds);
+      if (e3) throw e3;
+
+      const { error: e4 } = await supabase
+        .from("collections")
+        .delete()
+        .in("id", sourceIds);
+      if (e4) throw e4;
+
+      toast.success(
+        `Merged ${sourceIds.length} collection${sourceIds.length === 1 ? "" : "s"} into the kept ledger`,
+      );
+      onOpenChange(false);
+      onMerged?.();
+    } catch (err: any) {
+      toast.error("Could not merge collections", { description: err?.message });
+    } finally {
+      setSubmitting(false);
+    }
+  };
+
+  return (
+    <Dialog open={open} onOpenChange={onOpenChange}>
+      <DialogContent className="max-w-xl">
+        <DialogHeader>
+          <DialogTitle className="font-serif flex items-center gap-2">
+            <Merge className="h-4 w-4" /> Merge collections on this case
+          </DialogTitle>
+          <DialogDescription>
+            Combine multiple per-homeowner collections into a single ledger.
+            Ledger entries, payments, and workflow tasks are moved into the
+            kept collection. The merged-in collections are then deleted.
+          </DialogDescription>
+        </DialogHeader>
+
+        <div className="space-y-3">
+          {collections.length < 2 ? (
+            <Alert>
+              <AlertTriangle className="h-4 w-4" />
+              <AlertDescription>
+                This case needs at least 2 collections to merge.
+              </AlertDescription>
+            </Alert>
+          ) : (
+            <>
+              <div>
+                <Label>Keep this collection (target)</Label>
+                <Select value={keepId} onValueChange={setKeepId}>
+                  <SelectTrigger>
+                    <SelectValue placeholder="Pick the kept ledger" />
+                  </SelectTrigger>
+                  <SelectContent>
+                    {collections.map((c) => (
+                      <SelectItem key={c.id} value={c.id}>
+                        {labelOf(c)}
+                        {counts[c.id]
+                          ? ` · ${counts[c.id].entries} entries · ${counts[c.id].tasks} tasks`
+                          : ""}
+                      </SelectItem>
+                    ))}
+                  </SelectContent>
+                </Select>
+              </div>
+
+              <div>
+                <Label>Merge these into the kept ledger</Label>
+                <div className="border rounded-md max-h-72 overflow-y-auto mt-1 divide-y">
+                  {sources.length === 0 ? (
+                    <p className="p-3 text-sm text-muted-foreground italic">
+                      No other collections on this case.
+                    </p>
+                  ) : (
+                    sources.map((c) => (
+                      <label
+                        key={c.id}
+                        className="flex items-center gap-3 px-3 py-2 text-sm hover:bg-muted/50 cursor-pointer"
+                      >
+                        <Checkbox
+                          checked={mergeIds.has(c.id)}
+                          onCheckedChange={() => toggleSource(c.id)}
+                        />
+                        <div className="flex-1 min-w-0">
+                          <div className="flex items-center gap-2 flex-wrap">
+                            <span className="font-medium">{labelOf(c)}</span>
+                            <Badge variant="outline" className="text-[10px] capitalize">
+                              {c.status}
+                            </Badge>
+                          </div>
+                          <div className="text-xs text-muted-foreground">
+                            {loadingCounts
+                              ? "Loading…"
+                              : `${counts[c.id]?.entries ?? 0} ledger entries · ${counts[c.id]?.tasks ?? 0} tasks`}
+                          </div>
+                        </div>
+                      </label>
+                    ))
+                  )}
+                </div>
+              </div>
+
+              {mergeIds.size > 0 && (
+                <Alert variant="destructive">
+                  <AlertTriangle className="h-4 w-4" />
+                  <AlertDescription>
+                    This permanently deletes {mergeIds.size} collection
+                    {mergeIds.size === 1 ? "" : "s"} after moving their data.
+                    It cannot be undone.
+                  </AlertDescription>
+                </Alert>
+              )}
+            </>
+          )}
+        </div>
+
+        <DialogFooter>
+          <Button variant="outline" onClick={() => onOpenChange(false)}>
+            Cancel
+          </Button>
+          <Button
+            onClick={submit}
+            disabled={submitting || collections.length < 2 || !keepId || mergeIds.size === 0}
+          >
+            {submitting && <Loader2 className="h-4 w-4 mr-2 animate-spin" />}
+            Merge {mergeIds.size} into 1
+          </Button>
+        </DialogFooter>
+      </DialogContent>
+    </Dialog>
+  );
+}