diff --git a/weboob/tools/capabilities/bill/__init__.py b/weboob/tools/capabilities/bill/__init__.py
new file mode 100644
index 0000000000000000000000000000000000000000..e69de29bb2d1d6434b8b29ae775ad8c2e48c5391
diff --git a/weboob/tools/capabilities/bill/documents.py b/weboob/tools/capabilities/bill/documents.py
new file mode 100644
index 0000000000000000000000000000000000000000..25eb2439998397741ee43ae72cf252c51797376b
--- /dev/null
+++ b/weboob/tools/capabilities/bill/documents.py
@@ -0,0 +1,54 @@
+# -*- coding: utf-8 -*-
+
+# Copyright(C) 2020  Budget Insight
+#
+# This file is part of weboob.
+#
+# weboob is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# weboob is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with weboob. If not, see <http://www.gnu.org/licenses/>.
+
+from collections import OrderedDict
+
+
+__all__ = ['sorted_documents', 'merge_iterators']
+
+
+def sorted_documents(iterable):
+    """Sort an iterable of documents in reverse chronological order"""
+    return sorted(iterable, reverse=True, key=lambda doc: doc.date)
+
+
+def merge_iterators(*iterables):
+    """Merge documents iterators keeping sort order.
+
+    Each iterator must already be sorted in reverse chronological order.
+    """
+
+    def keyfunc(kv):
+        return kv[1].date
+
+    its = OrderedDict((iter(it), None) for it in iterables)
+    for k in list(its):
+        try:
+            its[k] = next(k)
+        except StopIteration:
+            del its[k]
+
+    while its:
+        k, v = max(its.items(), key=keyfunc)
+        yield v
+
+        try:
+            its[k] = next(k)
+        except StopIteration:
+            del its[k]