diff --git a/supabase/migrations/20260601140000_accounting_sync_bills.sql b/supabase/migrations/20260601140000_accounting_sync_bills.sql
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+-- Bidirectional bill sync between the main app and the Accounting platform.
+--   Forward: an approved/paid public.bills row (created by the bill-approvals
+--            flow) is mirrored into accounting.bills (Payables), creating the
+--            accounting vendor + a single line item.
+--   Back:    when an accounting.bills row is marked paid (paid_amount >= total),
+--            the linked public.bills is set status='paid' (+ paid_date,
+--            amount_paid) and its bill_approvals are marked paid.
+-- Scoped to associations with an accounting.companies row. Keyed by
+-- external_source='acmacc_bill' / 'acmacc_vendor', external_id = public row id.
+
+-- ---------------------------------------------------------------------------
+-- Find-or-create the accounting vendor mirroring a public vendor.
+-- Adopts an existing same-name accounting vendor before creating a new one.
+-- ---------------------------------------------------------------------------
+create or replace function accounting.ensure_vendor_for_public(_company_id uuid, _public_vendor_id uuid)
+returns uuid
+language plpgsql security definer set search_path to 'public','accounting'
+as $$
+declare _vid uuid; _name text; _email text; _phone text; _addr text;
+begin
+  if _public_vendor_id is null then return null; end if;
+
+  select id into _vid from accounting.vendors
+  where company_id=_company_id and external_source='acmacc_vendor' and external_id=_public_vendor_id::text;
+  if _vid is not null then return _vid; end if;
+
+  select name, email, phone, address into _name, _email, _phone, _addr
+  from public.vendors where id=_public_vendor_id;
+  if _name is null then _name := 'Vendor'; end if;
+
+  -- adopt an existing same-name vendor (avoid duplicates), else create
+  select id into _vid from accounting.vendors
+  where company_id=_company_id and lower(trim(name))=lower(trim(_name)) limit 1;
+  if _vid is not null then
+    update accounting.vendors
+      set external_source='acmacc_vendor', external_id=_public_vendor_id::text,
+          email=coalesce(email,_email), phone=coalesce(phone,_phone), address=coalesce(address,_addr),
+          updated_at=now()
+      where id=_vid;
+    return _vid;
+  end if;
+
+  insert into accounting.vendors (company_id, name, email, phone, address, external_source, external_id)
+  values (_company_id, _name, _email, _phone, _addr, 'acmacc_vendor', _public_vendor_id::text)
+  returning id into _vid;
+  return _vid;
+end;
+$$;
+
+-- Should a public bill of this status appear in accounting Payables?
+create or replace function accounting.bill_should_mirror(_status text)
+returns boolean language sql immutable as $$
+  select coalesce(lower(_status), '') not in
+    ('draft','pending','pending_approval','rejected','void','voided','cancelled','denied');
+$$;
+
+-- ---------------------------------------------------------------------------
+-- Forward: mirror one public.bills row into accounting.bills (idempotent).
+-- ---------------------------------------------------------------------------
+create or replace function accounting.sync_public_bill(_bill_id uuid)
+returns void
+language plpgsql security definer set search_path to 'public','accounting'
+as $$
+declare
+  b public.bills%rowtype;
+  _company_id uuid;
+  _vendor_id uuid;
+  _status accounting.bill_status;
+  _paid numeric; _tot numeric;
+  _acct_bill_id uuid;
+begin
+  select * into b from public.bills where id=_bill_id;
+  if not found then return; end if;
+
+  select id into _company_id from accounting.companies where association_id=b.association_id;
+  if _company_id is null then return; end if;
+
+  if not accounting.bill_should_mirror(b.status) then
+    delete from accounting.bills where company_id=_company_id and external_source='acmacc_bill' and external_id=b.id::text;
+    return;
+  end if;
+
+  _vendor_id := accounting.ensure_vendor_for_public(_company_id, b.vendor_id);
+  _paid := coalesce(b.amount_paid, 0);
+  _tot  := coalesce(b.amount, 0);
+  _status := (case when _paid >= _tot and _tot > 0 then 'paid'
+                   when _paid > 0 then 'partially_paid'
+                   else 'open' end)::accounting.bill_status;
+
+  insert into accounting.bills
+    (company_id, vendor_id, number, issue_date, due_date, status, subtotal, tax, total,
+     notes, paid_amount, attachment_url, external_source, external_id)
+  values
+    (_company_id, _vendor_id,
+     coalesce(nullif(b.invoice_number,''), 'BILL-' || left(replace(b.id::text,'-',''),8)),
+     b.bill_date, b.due_date, _status, _tot, 0, _tot,
+     b.description, _paid, b.attachment_url, 'acmacc_bill', b.id::text)
+  on conflict (company_id, external_source, external_id) where external_id is not null
+  do update set vendor_id=excluded.vendor_id, number=excluded.number, issue_date=excluded.issue_date,
+     due_date=excluded.due_date, status=excluded.status, subtotal=excluded.subtotal,
+     total=excluded.total, notes=excluded.notes, paid_amount=excluded.paid_amount,
+     attachment_url=excluded.attachment_url, updated_at=now()
+  returning id into _acct_bill_id;
+
+  if _acct_bill_id is null then
+    select id into _acct_bill_id from accounting.bills
+    where company_id=_company_id and external_source='acmacc_bill' and external_id=b.id::text;
+  end if;
+
+  -- Single line item mirroring the bill amount (refresh on each sync).
+  delete from accounting.bill_items where bill_id=_acct_bill_id;
+  insert into accounting.bill_items (bill_id, description, quantity, rate, amount)
+  values (_acct_bill_id, coalesce(nullif(b.description,''), 'Bill ' || coalesce(b.invoice_number,'')), 1, _tot, _tot);
+end;
+$$;
+
+-- ---------------------------------------------------------------------------
+-- Back: when an accounting bill is fully paid, reflect it on the public bill.
+-- ---------------------------------------------------------------------------
+create or replace function accounting.sync_accounting_bill_paid(_acct_bill_id uuid)
+returns void
+language plpgsql security definer set search_path to 'public','accounting'
+as $$
+declare ab accounting.bills%rowtype; _public_id uuid;
+begin
+  select * into ab from accounting.bills where id=_acct_bill_id;
+  if not found then return; end if;
+  if ab.external_source <> 'acmacc_bill' or ab.external_id is null then return; end if;
+  if not (coalesce(ab.paid_amount,0) >= coalesce(ab.total,0) and coalesce(ab.total,0) > 0) then return; end if;
+
+  _public_id := ab.external_id::uuid;
+  update public.bills
+    set status='paid', amount_paid=ab.total,
+        paid_date=coalesce(paid_date, current_date), updated_at=now()
+    where id=_public_id and status is distinct from 'paid';
+
+  update public.bill_approvals
+    set status='paid', updated_at=now()
+    where bill_id=_public_id and status is distinct from 'paid';
+end;
+$$;
+
+-- ---------------------------------------------------------------------------
+-- Triggers (error-swallowed).
+-- ---------------------------------------------------------------------------
+create or replace function accounting.tg_public_bill_sync()
+returns trigger
+language plpgsql security definer set search_path to 'public','accounting'
+as $$
+declare _company_id uuid;
+begin
+  begin
+    if tg_op='DELETE' then
+      select id into _company_id from accounting.companies where association_id=old.association_id;
+      if _company_id is not null then
+        delete from accounting.bills where company_id=_company_id and external_source='acmacc_bill' and external_id=old.id::text;
+      end if;
+      return old;
+    end if;
+    perform accounting.sync_public_bill(new.id);
+    return new;
+  exception when others then
+    raise warning 'accounting: public bill sync failed for %: %', coalesce(new.id, old.id), sqlerrm;
+    return coalesce(new, old);
+  end;
+end;
+$$;
+
+create or replace function accounting.tg_accounting_bill_paid_sync()
+returns trigger
+language plpgsql security definer set search_path to 'public','accounting'
+as $$
+begin
+  begin
+    -- only act when the paid position actually changed, to avoid loops
+    if old.paid_amount is distinct from new.paid_amount or old.total is distinct from new.total then
+      perform accounting.sync_accounting_bill_paid(new.id);
+    end if;
+  exception when others then
+    raise warning 'accounting: accounting bill paid sync failed for %: %', new.id, sqlerrm;
+  end;
+  return new;
+end;
+$$;
+
+drop trigger if exists trg_acct_sync_public_bill on public.bills;
+create trigger trg_acct_sync_public_bill
+  after insert or update or delete on public.bills
+  for each row execute function accounting.tg_public_bill_sync();
+
+drop trigger if exists trg_acct_bill_paid_back on accounting.bills;
+create trigger trg_acct_bill_paid_back
+  after update on accounting.bills
+  for each row execute function accounting.tg_accounting_bill_paid_sync();