diff --git a/core/src/main/java/place/sita/labelle/core/repository/inrepository/delta/DeltaService.java b/core/src/main/java/place/sita/labelle/core/repository/inrepository/delta/DeltaService.java
index d4914be..8617ffc 100644
--- a/core/src/main/java/place/sita/labelle/core/repository/inrepository/delta/DeltaService.java
+++ b/core/src/main/java/place/sita/labelle/core/repository/inrepository/delta/DeltaService.java
@@ -10,6 +10,7 @@
 import java.util.UUID;
 import java.util.stream.Collectors;
 
+import static place.sita.labelle.jooq.Tables.TAG_DELTA;
 import static place.sita.labelle.jooq.Tables.TAG_DELTA_CALC;
 
 @Service
@@ -21,6 +22,23 @@ public DeltaService(DSLContext dslContext) {
 		this.dslContext = dslContext;
 	}
 
+	@Transactional
+	public void addTagDelta(UUID imageId, String tag, String category, TagDeltaType added) {
+		// does tag delta for this image id, tag and category already exist?
+		dslContext.deleteFrom(TAG_DELTA)
+			.where(TAG_DELTA.IMAGE_ID.eq(imageId)
+				.and(TAG_DELTA.TAG.eq(tag))
+				.and(TAG_DELTA.CATEGORY.eq(category))
+			).execute();
+
+		dslContext.insertInto(TagDelta.TAG_DELTA)
+			.set(TagDelta.TAG_DELTA.IMAGE_ID, imageId)
+			.set(TagDelta.TAG_DELTA.TAG, tag)
+			.set(TagDelta.TAG_DELTA.CATEGORY, category)
+			.set(TagDelta.TAG_DELTA.ADDS, added == TagDeltaType.ADD)
+			.execute();
+	}
+
 	@Transactional
 	public void recalculateTagDeltas(Set<UUID> imageIds) {
 		dslContext.deleteFrom(TagDelta.TAG_DELTA)
diff --git a/gui-local/src/main/java/place/sita/labelle/gui/local/repositoryfx/TagDeltasComponentController.java b/gui-local/src/main/java/place/sita/labelle/gui/local/repositoryfx/TagDeltasComponentController.java
index 31d4459..5dd7b5c 100644
--- a/gui-local/src/main/java/place/sita/labelle/gui/local/repositoryfx/TagDeltasComponentController.java
+++ b/gui-local/src/main/java/place/sita/labelle/gui/local/repositoryfx/TagDeltasComponentController.java
@@ -143,12 +143,23 @@ public String toString() {
 	}
 
 	@FXML
-	void addDeltaButtonPress(ActionEvent event) {
-
+	public void addDeltaButtonPress(ActionEvent event) {
+		addDelta(DeltaType.ADD, deltaCategoryTextField.getText(), deltaEntryTextField.getText());
 	}
 
 	@FXML
-	void removeDeltaButtonPress(ActionEvent event) {
+	public void removeDeltaButtonPress(ActionEvent event) {
+		addDelta(DeltaType.REMOVE, deltaCategoryTextField.getText(), deltaEntryTextField.getText());
+	}
+
+	private void addDelta(DeltaType deltaType, String category, String tag) {
+		Threading.onSeparateThread(toolkit -> {
+			deltaService.addTagDelta(selected.id(), tag, category, map(deltaType));
+			toolkit.onFxThread(() -> {
+				// adding deltas has side effects that are too bothersome to calculate in view context
+				reloadDeltas();
+			});
+		});
 
 	}