diff --git a/libpretixsync/src/main/java/eu/pretix/libpretixsync/sqldelight/ClosingExtensions.kt b/libpretixsync/src/main/java/eu/pretix/libpretixsync/sqldelight/ClosingExtensions.kt
new file mode 100644
index 00000000..3d44b157
--- /dev/null
+++ b/libpretixsync/src/main/java/eu/pretix/libpretixsync/sqldelight/ClosingExtensions.kt
@@ -0,0 +1,26 @@
+package eu.pretix.libpretixsync.sqldelight
+
+import org.json.JSONObject
+import java.math.RoundingMode
+import java.text.DateFormat
+import java.text.SimpleDateFormat
+import java.util.TimeZone
+
+fun Closing.toJSON(): JSONObject {
+    val tz = TimeZone.getTimeZone("UTC")
+    val df: DateFormat = SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'")
+    df.timeZone = tz
+
+    val jo = JSONObject()
+    jo.put("closing_id", id)
+    jo.put("first_receipt", first_receipt)
+    jo.put("last_receipt", last_receipt)
+    jo.put("payment_sum", payment_sum?.setScale(2, RoundingMode.HALF_UP))
+    jo.put("payment_sum_cash", payment_sum_cash?.setScale(2, RoundingMode.HALF_UP))
+    jo.put("cash_counted", cash_counted?.setScale(2, RoundingMode.HALF_UP))
+    jo.put("datetime", df.format(datetime))
+    jo.put("invoice_settings", invoice_settings)
+    jo.put("cashier", cashier_numericid)
+    jo.put("data", if (json_data != null) JSONObject(json_data) else JSONObject())
+    return jo
+}
diff --git a/libpretixsync/src/main/java/eu/pretix/libpretixsync/sync/SyncManager.java b/libpretixsync/src/main/java/eu/pretix/libpretixsync/sync/SyncManager.java
index 3315aee0..fa05a9f0 100644
--- a/libpretixsync/src/main/java/eu/pretix/libpretixsync/sync/SyncManager.java
+++ b/libpretixsync/src/main/java/eu/pretix/libpretixsync/sync/SyncManager.java
@@ -3,6 +3,8 @@
 import eu.pretix.libpretixsync.api.*;
 import eu.pretix.libpretixsync.models.Question;
 import eu.pretix.libpretixsync.models.db.QuestionExtensionsKt;
+import eu.pretix.libpretixsync.sqldelight.Closing;
+import eu.pretix.libpretixsync.sqldelight.ClosingExtensionsKt;
 import eu.pretix.libpretixsync.sqldelight.QueuedCall;
 import eu.pretix.libpretixsync.sqldelight.QueuedCheckIn;
 import eu.pretix.libpretixsync.sqldelight.SyncDatabase;
@@ -20,7 +22,6 @@
 import eu.pretix.libpretixsync.SentryInterface;
 import eu.pretix.libpretixsync.config.ConfigStore;
 import eu.pretix.libpretixsync.db.Answer;
-import eu.pretix.libpretixsync.db.Closing;
 import eu.pretix.libpretixsync.db.QueuedOrder;
 import eu.pretix.libpretixsync.db.Receipt;
 import eu.pretix.libpretixsync.db.ReceiptLine;
@@ -672,10 +673,7 @@ protected void uploadOrders(ProgressFeedback feedback) throws SyncException {
     protected void uploadClosings(ProgressFeedback feedback) throws SyncException {
         sentry.addBreadcrumb("sync.queue", "Start closings upload");
 
-        List<Closing> closings = dataStore.select(Closing.class)
-                .where(Closing.OPEN.eq(false))
-                .and(Closing.SERVER_ID.isNull())
-                .get().toList();
+        List<Closing> closings = db.getClosingQueries().selectClosedWithoutServerId().executeAsList();
 
         try {
             int i = 0;
@@ -686,11 +684,10 @@ protected void uploadClosings(ProgressFeedback feedback) throws SyncException {
                 i++;
                 PretixApi.ApiResponse response = api.postResource(
                         api.organizerResourceUrl("posdevices/" + configStore.getPosId() + "/closings"),
-                        closing.toJSON()
+                        ClosingExtensionsKt.toJSON(closing)
                 );
                 if (response.getResponse().code() == 201) {
-                    closing.setServer_id(response.getData().getLong("closing_id"));
-                    dataStore.update(closing);
+                    db.getClosingQueries().updateServerId(response.getData().getLong("closing_id"), closing.getId());
                 } else {
                     throw new SyncException(response.getData().toString());
                 }
diff --git a/libpretixsync/src/main/sqldelight/common/eu/pretix/libpretixsync/sqldelight/Closing.sq b/libpretixsync/src/main/sqldelight/common/eu/pretix/libpretixsync/sqldelight/Closing.sq
index 1e0354c4..9fb4234b 100644
--- a/libpretixsync/src/main/sqldelight/common/eu/pretix/libpretixsync/sqldelight/Closing.sq
+++ b/libpretixsync/src/main/sqldelight/common/eu/pretix/libpretixsync/sqldelight/Closing.sq
@@ -8,6 +8,13 @@ SELECT *
 FROM Closing
 WHERE server_id = ?;
 
+selectClosedWithoutServerId:
+SELECT *
+FROM Closing
+WHERE
+    open = FALSE
+    AND server_id IS NULL;
+
 insert:
 INSERT INTO Closing (
     cash_counted,
@@ -40,3 +47,9 @@ INSERT INTO Closing (
     ?,
     ?
 );
+
+updateServerId:
+UPDATE Closing
+SET
+    server_id = ?
+WHERE id = ?;