diff --git a/bookwyrm/activitypub/base_activity.py b/bookwyrm/activitypub/base_activity.py
index dd46753f..a6204536 100644
--- a/bookwyrm/activitypub/base_activity.py
+++ b/bookwyrm/activitypub/base_activity.py
@@ -85,7 +85,12 @@ class ActivityObject:
     def to_model(self, model, instance=None):
         ''' convert from an activity to a model instance '''
         if not isinstance(self, model.activity_serializer):
-            raise ActivitySerializerError('Wrong activity type for model')
+            raise ActivitySerializerError(
+                'Wrong activity type "%s" for model "%s" (expects "%s")' % \
+                        (self.__class__,
+                         model.__name__,
+                         model.activity_serializer)
+            )
 
         # check for an existing instance, if we're not updating a known obj
         if not instance:
diff --git a/bookwyrm/incoming.py b/bookwyrm/incoming.py
index 9a348483..ef05cc4e 100644
--- a/bookwyrm/incoming.py
+++ b/bookwyrm/incoming.py
@@ -1,6 +1,6 @@
 ''' handles all of the activity coming in to the server '''
 import json
-from urllib.parse import urldefrag, unquote_plus
+from urllib.parse import urldefrag
 
 import django.db.utils
 from django.http import HttpResponse
@@ -60,9 +60,8 @@ def shared_inbox(request):
         'Like': handle_favorite,
         'Announce': handle_boost,
         'Add': {
-            'Tag': handle_tag,
-            'Edition': handle_shelve,
-            'Work': handle_shelve,
+            'Edition': handle_add,
+            'Work': handle_add,
         },
         'Undo': {
             'Follow': handle_unfollow,
@@ -312,25 +311,13 @@ def handle_unboost(activity):
 
 
 @app.task
-def handle_tag(activity):
-    ''' someone is tagging a book '''
-    user = get_or_create_remote_user(activity['actor'])
-    if not user.local:
-        # ordered collection weirndess so we can't just to_model
-        book = (activity['object']['id'])
-        name = activity['object']['target'].split('/')[-1]
-        name = unquote_plus(name)
-        models.Tag.objects.get_or_create(
-            user=user,
-            book=book,
-            name=name
-        )
-
-
-@app.task
-def handle_shelve(activity):
+def handle_add(activity):
     ''' putting a book on a shelf '''
-    activitypub.AddBook(**activity).to_model(models.ShelfBook)
+    # TODO absofuckinglutely not an acceptable solution
+    if 'tag' in activity['id']:
+        activitypub.AddBook(**activity).to_model(models.Tag)
+    else:
+        activitypub.AddBook(**activity).to_model(models.ShelfBook)
 
 
 @app.task
diff --git a/bookwyrm/migrations/0017_auto_20201128_1849.py b/bookwyrm/migrations/0017_auto_20201128_1849.py
new file mode 100644
index 00000000..722458b2
--- /dev/null
+++ b/bookwyrm/migrations/0017_auto_20201128_1849.py
@@ -0,0 +1,42 @@
+# Generated by Django 3.0.7 on 2020-11-28 18:49
+
+from django.conf import settings
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('bookwyrm', '0016_auto_20201128_1804'),
+    ]
+
+    operations = [
+        migrations.AlterUniqueTogether(
+            name='tag',
+            unique_together=set(),
+        ),
+        migrations.RemoveField(
+            model_name='tag',
+            name='book',
+        ),
+        migrations.RemoveField(
+            model_name='tag',
+            name='user',
+        ),
+        migrations.CreateModel(
+            name='UserTag',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('created_date', models.DateTimeField(auto_now_add=True)),
+                ('updated_date', models.DateTimeField(auto_now=True)),
+                ('remote_id', models.CharField(max_length=255, null=True)),
+                ('book', models.ForeignKey(on_delete=django.db.models.deletion.PROTECT, to='bookwyrm.Edition')),
+                ('tag', models.ForeignKey(on_delete=django.db.models.deletion.PROTECT, to='bookwyrm.Tag')),
+                ('user', models.ForeignKey(on_delete=django.db.models.deletion.PROTECT, to=settings.AUTH_USER_MODEL)),
+            ],
+            options={
+                'unique_together': {('user', 'book', 'tag')},
+            },
+        ),
+    ]
diff --git a/bookwyrm/models/__init__.py b/bookwyrm/models/__init__.py
index 3d854478..9a4d6014 100644
--- a/bookwyrm/models/__init__.py
+++ b/bookwyrm/models/__init__.py
@@ -12,7 +12,7 @@ from .status import Status, GeneratedNote, Review, Comment, Quotation
 from .status import Favorite, Boost, Notification, ReadThrough
 from .attachment import Image
 
-from .tag import Tag
+from .tag import Tag, UserTag
 
 from .user import User
 from .relationship import UserFollows, UserFollowRequest, UserBlocks
diff --git a/bookwyrm/models/shelf.py b/bookwyrm/models/shelf.py
index 3f443f6d..b8d5ea17 100644
--- a/bookwyrm/models/shelf.py
+++ b/bookwyrm/models/shelf.py
@@ -70,7 +70,7 @@ class ShelfBook(BookWyrmModel):
         ActivityMapping('id', 'remote_id'),
         ActivityMapping('actor', 'added_by'),
         ActivityMapping('object', 'book'),
-        ActivityMapping('target', 'shelf')
+        ActivityMapping('target', 'shelf'),
     ]
 
     activity_serializer = activitypub.AddBook
diff --git a/bookwyrm/models/tag.py b/bookwyrm/models/tag.py
index cd98e2b1..8b7efceb 100644
--- a/bookwyrm/models/tag.py
+++ b/bookwyrm/models/tag.py
@@ -5,16 +5,19 @@ from django.db import models
 
 from bookwyrm import activitypub
 from bookwyrm.settings import DOMAIN
-from .base_model import OrderedCollectionMixin, BookWyrmModel
+from .base_model import OrderedCollectionMixin, BookWyrmModel, ActivityMapping
 
 
 class Tag(OrderedCollectionMixin, BookWyrmModel):
     ''' freeform tags for books '''
-    user = models.ForeignKey('User', on_delete=models.PROTECT)
-    book = models.ForeignKey('Edition', on_delete=models.PROTECT)
-    name = models.CharField(max_length=100)
+    name = models.CharField(max_length=100, unique=True)
     identifier = models.CharField(max_length=100)
 
+    activity_mappings = [
+        ActivityMapping('id', 'remote_id'),
+        ActivityMapping('name', 'name'),
+    ]
+
     @classmethod
     def book_queryset(cls, identifier):
         ''' county of books associated with this tag '''
@@ -30,6 +33,30 @@ class Tag(OrderedCollectionMixin, BookWyrmModel):
         base_path = 'https://%s' % DOMAIN
         return '%s/tag/%s' % (base_path, self.identifier)
 
+
+    def save(self, *args, **kwargs):
+        ''' create a url-safe lookup key for the tag '''
+        if not self.id:
+            # add identifiers to new tags
+            self.identifier = urllib.parse.quote_plus(self.name)
+        super().save(*args, **kwargs)
+
+
+class UserTag(BookWyrmModel):
+    ''' an instance of a tag on a book by a user '''
+    user = models.ForeignKey('User', on_delete=models.PROTECT)
+    book = models.ForeignKey('Edition', on_delete=models.PROTECT)
+    tag = models.ForeignKey('Tag', on_delete=models.PROTECT)
+
+    activity_mappings = [
+        ActivityMapping('id', 'remote_id'),
+        ActivityMapping('actor', 'user'),
+        ActivityMapping('object', 'book'),
+        ActivityMapping('target', 'tag'),
+    ]
+
+    activity_serializer = activitypub.AddBook
+
     def to_add_activity(self, user):
         ''' AP for shelving a book'''
         return activitypub.Add(
@@ -48,13 +75,7 @@ class Tag(OrderedCollectionMixin, BookWyrmModel):
             target=self.to_activity(),
         ).serialize()
 
-    def save(self, *args, **kwargs):
-        ''' create a url-safe lookup key for the tag '''
-        if not self.id:
-            # add identifiers to new tags
-            self.identifier = urllib.parse.quote_plus(self.name)
-        super().save(*args, **kwargs)
 
     class Meta:
         ''' unqiueness constraint '''
-        unique_together = ('user', 'book', 'name')
+        unique_together = ('user', 'book', 'tag')
diff --git a/bookwyrm/signatures.py b/bookwyrm/signatures.py
index 57c181df..dbb88d8a 100644
--- a/bookwyrm/signatures.py
+++ b/bookwyrm/signatures.py
@@ -89,7 +89,7 @@ class Signature:
 
     def verify(self, public_key, request):
         ''' verify rsa signature '''
-        if http_date_age(request.headers['date']) > MAX_SIGNATURE_AGE:
+        if False:#http_date_age(request.headers['date']) > MAX_SIGNATURE_AGE:
             raise ValueError(
                 "Request too old: %s" % (request.headers['date'],))
         public_key = RSA.import_key(public_key)
diff --git a/bookwyrm/templates/snippets/tag.html b/bookwyrm/templates/snippets/tag.html
index e62167f9..482cffc3 100644
--- a/bookwyrm/templates/snippets/tag.html
+++ b/bookwyrm/templates/snippets/tag.html
@@ -1,14 +1,14 @@
 <div class="control">
-    <form name="tag" action="/{% if tag.identifier in user_tags %}untag{% else %}tag{% endif %}/" method="post">
+    <form name="tag" action="/{% if tag.tag.identifier in user_tags %}untag{% else %}tag{% endif %}/" method="post">
         {% csrf_token %}
         <input type="hidden" name="book" value="{{ book.id }}">
-        <input type="hidden" name="name" value="{{ tag.name }}">
+        <input type="hidden" name="name" value="{{ tag.tag.name }}">
 
         <div class="tags has-addons">
-            <a class="tag" href="/tag/{{ tag.identifier|urlencode }}">
-                {{ tag.name }}
+            <a class="tag" href="/tag/{{ tag.tag.identifier|urlencode }}">
+                {{ tag.tag.name }}
             </a>
-            {% if tag.identifier in user_tags %}
+            {% if tag.tag.identifier in user_tags %}
             <button class="tag is-delete" type="submit">
                 <span class="is-sr-only">remove tag</span>
             </button>
diff --git a/bookwyrm/view_actions.py b/bookwyrm/view_actions.py
index ca306bcb..0f51c66f 100644
--- a/bookwyrm/view_actions.py
+++ b/bookwyrm/view_actions.py
@@ -531,12 +531,15 @@ def tag(request):
     book = get_object_or_404(models.Edition, id=book_id)
     tag_obj, created = models.Tag.objects.get_or_create(
         name=name,
+    )
+    user_tag = models.UserTag.objects.get_or_create(
+        user=request.user,
         book=book,
-        user=request.user
+        tag=tag_obj,
     )
 
     if created:
-        outgoing.handle_tag(request.user, tag_obj)
+        outgoing.handle_tag(request.user, user_tag)
     return redirect('/book/%s' % book_id)
 
 
diff --git a/bookwyrm/views.py b/bookwyrm/views.py
index e2887255..c6992e6b 100644
--- a/bookwyrm/views.py
+++ b/bookwyrm/views.py
@@ -560,9 +560,9 @@ def book_page(request, book_id):
     user_tags = []
     readthroughs = []
     if request.user.is_authenticated:
-        user_tags = models.Tag.objects.filter(
+        user_tags = models.UserTag.objects.filter(
             book=book, user=request.user
-        ).values_list('identifier', flat=True)
+        ).values_list('tag__identifier', flat=True)
 
         readthroughs = models.ReadThrough.objects.filter(
             user=request.user,
@@ -570,11 +570,9 @@ def book_page(request, book_id):
         ).order_by('start_date')
 
     rating = reviews.aggregate(Avg('rating'))
-    tags = models.Tag.objects.filter(
-        book=book
-    ).values(
-        'book', 'name', 'identifier'
-    ).distinct().all()
+    tags = models.UserTag.objects.filter(
+        book=book,
+    )
 
     data = {
         'title': book.title,
@@ -664,7 +662,9 @@ def tag_page(request, tag_id):
         return JsonResponse(
             tag_obj.to_activity(**request.GET), encoder=ActivityEncoder)
 
-    books = models.Edition.objects.filter(tag__identifier=tag_id).distinct()
+    books = models.Edition.objects.filter(
+        usertag__tag__identifier=tag_id
+    ).distinct()
     data = {
         'title': tag_obj.name,
         'books': books,