diff --git a/swh/deposit/api/common.py b/swh/deposit/api/common.py
--- a/swh/deposit/api/common.py
+++ b/swh/deposit/api/common.py
@@ -27,7 +27,12 @@
 from swh.deposit.models import Deposit
 from swh.deposit.utils import compute_metadata_context
 from swh.model import hashutil
-from swh.model.identifiers import ExtendedSWHID, QualifiedSWHID, ValidationError
+from swh.model.identifiers import (
+    ExtendedObjectType,
+    ExtendedSWHID,
+    QualifiedSWHID,
+    ValidationError,
+)
 from swh.model.model import (
     MetadataAuthority,
     MetadataAuthorityType,
@@ -681,7 +686,43 @@
 
             target_swhid = extended_swhid_from_qualified(swhid_reference)
 
-        # store that metadata to the metadata storage
+        # Check the target object already exists in the archive
+        if target_swhid.object_type in (ExtendedObjectType.CONTENT,):
+            if list(
+                self.storage.content_missing_per_sha1_git([target_swhid.object_id])
+            ):
+                raise DepositError(
+                    BAD_REQUEST,
+                    f"Cannot load metadata on {target_swhid}, this content "
+                    f"object does not exist in the archive (yet?).",
+                )
+        elif target_swhid.object_type in (
+            ExtendedObjectType.DIRECTORY,
+            ExtendedObjectType.REVISION,
+            ExtendedObjectType.RELEASE,
+            ExtendedObjectType.SNAPSHOT,
+        ):
+            target_type_name = target_swhid.object_type.name.lower()
+            method = getattr(self.storage, target_type_name + "_missing")
+            if list(method([target_swhid.object_id])):
+                raise DepositError(
+                    BAD_REQUEST,
+                    f"Cannot load metadata on {target_swhid}, this {target_type_name} "
+                    f"object does not exist in the archive (yet?).",
+                )
+        elif target_swhid.object_type in (ExtendedObjectType.ORIGIN,):
+            if None in list(self.storage.origin_get_by_sha1([target_swhid.object_id])):
+                raise DepositError(
+                    BAD_REQUEST,
+                    f"Cannot load metadata on origin, it is not (yet?) known to the "
+                    f"archive.",
+                )
+        else:
+            raise DepositError(
+                BAD_REQUEST,
+                "Cannot deposit metadata on {target_swhid.object_type.value}.",
+            )
+
         metadata_object = RawExtrinsicMetadata(
             target=target_swhid,  # core swhid or origin
             discovery_date=deposit_request.date,
diff --git a/swh/deposit/config.py b/swh/deposit/config.py
--- a/swh/deposit/config.py
+++ b/swh/deposit/config.py
@@ -104,6 +104,7 @@
             "version": __version__,
             "configuration": {"sword_version": "2"},
         }
+        self.storage: StorageInterface = get_storage(**self.config["storage"])
         self.storage_metadata: StorageInterface = get_storage(
             **self.config["storage_metadata"]
         )
diff --git a/swh/deposit/tests/api/test_collection_post_atom.py b/swh/deposit/tests/api/test_collection_post_atom.py
--- a/swh/deposit/tests/api/test_collection_post_atom.py
+++ b/swh/deposit/tests/api/test_collection_post_atom.py
@@ -7,6 +7,7 @@
 
 from io import BytesIO
 import uuid
+import warnings
 
 import attr
 from django.urls import reverse_lazy as reverse
@@ -23,8 +24,16 @@
 from swh.deposit.parsers import parse_xml
 from swh.deposit.tests.common import post_atom
 from swh.deposit.utils import compute_metadata_context, extended_swhid_from_qualified
-from swh.model.identifiers import QualifiedSWHID
+from swh.model.hypothesis_strategies import (
+    directories,
+    present_contents,
+    releases,
+    revisions,
+    snapshots,
+)
+from swh.model.identifiers import ObjectType, QualifiedSWHID
 from swh.model.model import (
+    Content,
     MetadataAuthority,
     MetadataAuthorityType,
     MetadataFetcher,
@@ -34,6 +43,30 @@
 from swh.storage.interface import PagedResult
 
 
+def _insert_object(swh_storage, swhid):
+    """Insert an object with the given swhid in the archive"""
+    if swhid.object_type == ObjectType.CONTENT:
+        with warnings.catch_warnings():
+            # hypothesis doesn't like us using .example(), but we know what we're doing
+            warnings.simplefilter("ignore")
+            obj = present_contents().example()
+        swh_storage.content_add([attr.evolve(obj, sha1_git=swhid.object_id)])
+    else:
+        object_type_name = swhid.object_type.name.lower()
+        strategy = {
+            "directory": directories,
+            "revision": revisions,
+            "release": releases,
+            "snapshot": snapshots,
+        }[object_type_name]
+        method = getattr(swh_storage, object_type_name + "_add")
+        with warnings.catch_warnings():
+            # hypothesis doesn't like us using .example(), but we know what we're doing
+            warnings.simplefilter("ignore")
+            obj = strategy().example()
+        method([attr.evolve(obj, id=swhid.object_id)])
+
+
 def test_post_deposit_atom_201_even_with_decimal(
     authenticated_client, deposit_collection, atom_dataset
 ):
@@ -478,13 +511,15 @@
     xml_data = atom_dataset["entry-data-with-swhid"].format(swhid=swhid)
     deposit_client = authenticated_client.deposit_client
 
+    _insert_object(swh_storage, swhid_reference)
+
     response = post_atom(
         authenticated_client,
         reverse(COL_IRI, args=[deposit_collection.name]),
         data=xml_data,
     )
 
-    assert response.status_code == status.HTTP_201_CREATED
+    assert response.status_code == status.HTTP_201_CREATED, response.content.decode()
     response_content = parse_xml(BytesIO(response.content))
 
     # Ensure the deposit is finalized
@@ -558,13 +593,14 @@
     xml_data = atom_dataset["entry-data-with-origin-reference"].format(url=url)
     origin_swhid = Origin(url).swhid()
     deposit_client = authenticated_client.deposit_client
+    swh_storage.origin_add([Origin(url)])
     response = post_atom(
         authenticated_client,
         reverse(COL_IRI, args=[deposit_collection.name]),
         data=xml_data,
     )
 
-    assert response.status_code == status.HTTP_201_CREATED
+    assert response.status_code == status.HTTP_201_CREATED, response.content.decode()
     response_content = parse_xml(BytesIO(response.content))
     # Ensure the deposit is finalized
     deposit_id = int(response_content["swh:deposit_id"])
@@ -622,3 +658,66 @@
         next_page_token=None,
     )
     assert deposit.complete_date == discovery_date
+
+
+@pytest.mark.parametrize(
+    "swhid",
+    [
+        "swh:1:cnt:01b5c8cc985d190b5a7ef4878128ebfdc2358f49",
+        "swh:1:dir:11b5c8cc985d190b5a7ef4878128ebfdc2358f49",
+        "swh:1:rev:21b5c8cc985d190b5a7ef4878128ebfdc2358f49",
+        "swh:1:rel:31b5c8cc985d190b5a7ef4878128ebfdc2358f49",
+        "swh:1:snp:41b5c8cc985d190b5a7ef4878128ebfdc2358f49",
+        "swh:1:cnt:51b5c8cc985d190b5a7ef4878128ebfdc2358f49;origin=h://g.c/o/repo",
+        "swh:1:dir:c4993c872593e960dc84e4430dbbfbc34fd706d0;origin=https://inria.halpreprod.archives-ouvertes.fr/hal-01243573;visit=swh:1:snp:0175049fc45055a3824a1675ac06e3711619a55a;anchor=swh:1:rev:b5f505b005435fa5c4fa4c279792bd7b17167c04;path=/",  # noqa
+        "swh:1:rev:71b5c8cc985d190b5a7ef4878128ebfdc2358f49;origin=h://g.c/o/repo",
+        "swh:1:rel:81b5c8cc985d190b5a7ef4878128ebfdc2358f49;origin=h://g.c/o/repo",
+        "swh:1:snp:91b5c8cc985d190b5a7ef4878128ebfdc2358f49;origin=h://g.c/o/repo",
+    ],
+)
+def test_deposit_metadata_unknown_swhid(
+    swhid, authenticated_client, deposit_collection, atom_dataset, swh_storage,
+):
+    """Posting a swhid reference is rejected if the referenced object is unknown
+
+    """
+    swhid_reference = QualifiedSWHID.from_string(swhid)
+    swhid_target = extended_swhid_from_qualified(swhid_reference)
+
+    xml_data = atom_dataset["entry-data-with-swhid"].format(swhid=swhid)
+    deposit_client = authenticated_client.deposit_client
+
+    response = post_atom(
+        authenticated_client,
+        reverse(COL_IRI, args=[deposit_collection.name]),
+        data=xml_data,
+    )
+
+    assert (
+        response.status_code == status.HTTP_400_BAD_REQUEST
+    ), response.content.decode()
+    response_content = parse_xml(BytesIO(response.content))
+    assert "object does not exist" in response_content["sword:error"]["atom:summary"]
+
+
+def test_deposit_metadata_unknown_origin(
+    authenticated_client, deposit_collection, atom_dataset, swh_storage,
+):
+    """Posting a swhid reference is stored on raw extrinsic metadata storage
+
+    """
+    url = "https://gitlab.org/user/repo"
+    xml_data = atom_dataset["entry-data-with-origin-reference"].format(url=url)
+    origin_swhid = Origin(url).swhid()
+    deposit_client = authenticated_client.deposit_client
+    response = post_atom(
+        authenticated_client,
+        reverse(COL_IRI, args=[deposit_collection.name]),
+        data=xml_data,
+    )
+
+    assert (
+        response.status_code == status.HTTP_400_BAD_REQUEST
+    ), response.content.decode()
+    response_content = parse_xml(BytesIO(response.content))
+    assert "known to the archive" in response_content["sword:error"]["atom:summary"]
diff --git a/swh/deposit/tests/conftest.py b/swh/deposit/tests/conftest.py
--- a/swh/deposit/tests/conftest.py
+++ b/swh/deposit/tests/conftest.py
@@ -88,6 +88,7 @@
         "extraction_dir": "/tmp/swh-deposit/test/extraction-dir",
         "checks": False,
         "scheduler": {"cls": "local", **swh_scheduler_config,},
+        "storage": swh_storage_backend_config,
         "storage_metadata": swh_storage_backend_config,
     }