diff --git a/supabase/functions/buildium-payee-backfill/index.ts b/supabase/functions/buildium-payee-backfill/index.ts
index a1d987d..65fafab 100644
--- a/supabase/functions/buildium-payee-backfill/index.ts
+++ b/supabase/functions/buildium-payee-backfill/index.ts
@@ -298,6 +298,51 @@ Deno.serve(async (req) => {
       if (name) { payeeById.set(id, name); byType[type].named++; }
     }
 
+    // partymap mode: resolve each Buildium tx to a LOCAL vendor/customer id and
+    // stage it (accounting.buildium_party_map) so the materialized bank register
+    // (accounting.transactions) can be backfilled in SQL by bridging tx→JE.
+    //   vendor   : Payee.Type=Vendor  → match Payee.Name to accounting.vendors.name
+    //   customer : tx.UnitNumber      → match to accounting.customers.unit_number
+    if (mode === "partymap") {
+      const vendorByName = new Map<string, string>();
+      for (const v of (await supabase.schema("accounting").from("vendors").select("id,name").eq("company_id", companyId)).data ?? [])
+        if (v.name) vendorByName.set(norm(v.name), v.id);
+      const customerByUnitNo = new Map<string, string>();
+      for (const c of (await supabase.schema("accounting").from("customers").select("id,unit_number").eq("company_id", companyId)).data ?? [])
+        if (c.unit_number) customerByUnitNo.set(norm(c.unit_number), c.id);
+
+      const rows: any[] = [];
+      let vendorHits = 0, customerHits = 0;
+      for (const tx of txns) {
+        const id = String(tx?.Id ?? "");
+        if (!id) continue;
+        const name = payeeById.get(id) ?? null;
+        const payeeType = String(tx?.PaymentDetail?.Payee?.Type ?? "");
+        let vendor_id: string | null = null;
+        let customer_id: string | null = null;
+        if (payeeType === "Vendor" && name) vendor_id = vendorByName.get(norm(name)) ?? null;
+        const unitNo = tx?.UnitNumber;
+        if (!vendor_id && typeof unitNo === "string" && unitNo.trim()) customer_id = customerByUnitNo.get(norm(unitNo)) ?? null;
+        // owner payment with no UnitNumber: try the payee name against customers
+        if (!vendor_id && !customer_id && name && payeeType && payeeType !== "Vendor") {
+          // fall through — name match handled in SQL if needed; leave null here
+        }
+        if (vendor_id) vendorHits++;
+        if (customer_id) customerHits++;
+        if (name || vendor_id || customer_id)
+          rows.push({ company_id: companyId, external_id: id, party_name: name, vendor_id, customer_id, party_type: payeeType || null });
+      }
+      // Upsert in batches.
+      let staged = 0;
+      for (let i = 0; i < rows.length; i += 500) {
+        const batch = rows.slice(i, i + 500);
+        const { error } = await supabase.schema("accounting").from("buildium_party_map").upsert(batch, { onConflict: "company_id,external_id" });
+        if (error) throw error;
+        staged += batch.length;
+      }
+      return json({ mode, company: company.name, window: [dateFrom, dateTo], txns: txns.length, staged, vendorHits, customerHits });
+    }
+
     // Load this company's imported entries and compute the new description.
     const entries: { id: string; external_id: string; description: string }[] = [];
     for (let offset = 0; ; offset += 1000) {
diff --git a/supabase/migrations/20260615180000_buildium_party_map_staging.sql b/supabase/migrations/20260615180000_buildium_party_map_staging.sql
new file mode 100644
index 0000000..fef92e6
--- /dev/null
+++ b/supabase/migrations/20260615180000_buildium_party_map_staging.sql
@@ -0,0 +1,19 @@
+-- Staging table for the Buildium payee/payor register backfill.
+-- Maps a Buildium GL transaction id to the resolved local vendor/customer and
+-- the party name, so the materialized bank register (accounting.transactions)
+-- of imported-GL companies can be backfilled by bridging transaction → journal
+-- entry (by bank line) → this map. Populated by the buildium-payee-backfill
+-- edge function ("partymap" mode).
+create table if not exists accounting.buildium_party_map (
+  company_id uuid not null,
+  external_id text not null,
+  party_name text,
+  vendor_id uuid,
+  customer_id uuid,
+  party_type text,
+  updated_at timestamptz not null default now(),
+  primary key (company_id, external_id)
+);
+
+comment on table accounting.buildium_party_map is
+  'Staging: Buildium GL transaction id -> resolved local vendor/customer + name, used to backfill the materialized bank register (accounting.transactions) for imported companies.';