diff --git a/.env b/.env
index 75a7eacd..649bfc58 100644
--- a/.env
+++ b/.env
@@ -7,4 +7,7 @@ ADAMRMS_EMAIL=
 ADAMRMS_PASSWORD=
 ADAMRMS_BASE=https://dash.adam-rms.com
 ADAMRMS_PROJECT_TYPE_ID=18
+ADAMRMS_TENTATIVE_STATUS_ID=1051
+ADAMRMS_CONFIRMED_STATUS_ID=1053
+ADAMRMS_CANCELLED_STATUS_ID=1058
 SESSION_SECRET=change me
diff --git a/app/(authenticated)/calendar/[eventID]/EventActionsUI.tsx b/app/(authenticated)/calendar/[eventID]/EventActionsUI.tsx
index de1c67c5..205ee790 100644
--- a/app/(authenticated)/calendar/[eventID]/EventActionsUI.tsx
+++ b/app/(authenticated)/calendar/[eventID]/EventActionsUI.tsx
@@ -95,7 +95,23 @@ export function EventActionsUI(props: { event: EventObjectType }) {
         },
         onConfirm() {
           startTransition(async () => {
-            await reinstateEvent(props.event.event_id);
+            const result = await reinstateEvent(props.event.event_id);
+            if (!result.ok) {
+              modals.openModal({
+                id: "reinstate-error",
+                title: "Error",
+                children: (
+                  <>
+                    <Text>{result.errors?.root ?? `Unknown error (${JSON.stringify(result)})`}</Text>
+                    <Button
+                      onClick={() => modals.closeModal("reinstate-error")}
+                    >
+                      Close
+                    </Button>
+                  </>
+                ),
+              });
+            }
           });
         },
       });
diff --git a/app/(authenticated)/calendar/[eventID]/actions.ts b/app/(authenticated)/calendar/[eventID]/actions.ts
index 2da706b1..3ae39a61 100644
--- a/app/(authenticated)/calendar/[eventID]/actions.ts
+++ b/app/(authenticated)/calendar/[eventID]/actions.ts
@@ -220,7 +220,25 @@ export async function reinstateEvent(eventID: number) {
     };
   }
 
-  await Calendar.reinstateEvent(eventID);
+  const result = await Calendar.reinstateEvent(eventID);
+  if (!result.ok) {
+    switch (result.error) {
+      case "kit_clash":
+        return {
+          ok: false,
+          errors: {
+            root: "Reinstating this production would result in a kit clash. Please contact the Tech Team.",
+          },
+        };
+      default:
+        return {
+          ok: false,
+          errors: {
+            root: "An unknown error occurred (" + result.error + ")",
+          },
+        };
+    };
+  }
 
   revalidatePath(`/calendar/${event.event_id}`);
   revalidatePath("/calendar");
diff --git a/features/calendar/adamRMS.ts b/features/calendar/adamRMS.ts
index e1e10d53..76f37e94 100644
--- a/features/calendar/adamRMS.ts
+++ b/features/calendar/adamRMS.ts
@@ -31,6 +31,11 @@ export async function addProjectToAdamRMS(
     event.end_date,
     "deliver_dates",
   );
+  await AdamRMS.setProjectStatus(
+    projectId,
+    // No idea why you'd link a cancelled project to the RMS, but you do you...
+    event.is_cancelled ? "cancelled" : event.is_tentative ? "tentative" : "confirmed",
+  );
   await prisma.event.update({
     where: {
       event_id: eventID,
@@ -85,6 +90,10 @@ export async function linkAdamRMS(eventID: number, projectID: number) {
     event.end_date,
     "dates",
   );
+  await AdamRMS.setProjectStatus(
+    projectID,
+    event.is_cancelled ? "cancelled" : event.is_tentative ? "tentative" : "confirmed",
+  );
   await prisma.event.update({
     where: {
       event_id: eventID,
diff --git a/features/calendar/events.ts b/features/calendar/events.ts
index 0e1dba02..292ed14f 100644
--- a/features/calendar/events.ts
+++ b/features/calendar/events.ts
@@ -195,9 +195,9 @@ export async function updateEvent(
     // We use a raw query to get the event info so that we can SELECT FOR UPDATE,
     // otherwise this risks a race condition.
     const events = await $db.$queryRaw<
-      { adam_rms_project_id: number | null; start_date: Date; end_date: Date }[]
+      { adam_rms_project_id: number | null; start_date: Date; end_date: Date; is_tentative: boolean; is_cancelled: boolean; }[]
     >`
-      SELECT adam_rms_project_id, start_date, end_date FROM events WHERE event_id = ${eventID} FOR UPDATE`;
+      SELECT adam_rms_project_id, start_date, end_date, is_tentative, is_cancelled FROM events WHERE event_id = ${eventID} FOR UPDATE`;
     if (events.length === 0) {
       throw new Error("Event not found");
     }
@@ -207,6 +207,8 @@ export async function updateEvent(
     // This is because AdamRMS will reject the request if the dates would cause a kit clash.
     // We change the "deliver dates" first, because this actually triggers the kit clash check.
     // Then if it succeeds we update it locally and update the event dates to match.
+    // Similarly, if the status has changed, we need to update that, as un-cancelling an event
+    // can have the same effect.
     if (
       event.adam_rms_project_id &&
       (event.start_date.getTime() !== data.start_date.getTime() ||
@@ -222,6 +224,13 @@ export async function updateEvent(
         return { ok: false, error: "kit_clash" };
       }
     }
+
+    // It's not possible to reinstate an even through this function, so we don't need to worry about
+    // the status changing from cancelled to uncancelled. In other words, cancelled trumps tentative.
+    if (!event.is_cancelled && event.adam_rms_project_id && event.is_tentative !== data.is_tentative) {
+      await AdamRMS.setProjectStatus(event.adam_rms_project_id, data.is_tentative ? "tentative" : "confirmed");
+    }
+
     const result = await $db.event.update({
       where: {
         event_id: eventID,
@@ -288,25 +297,51 @@ export async function updateEventAttendeeStatus(
 }
 
 export async function cancelEvent(eventID: number) {
-  await prisma.event.update({
+  const res = await prisma.event.update({
     where: {
       event_id: eventID,
     },
     data: {
       is_cancelled: true,
     },
+    select: {
+      adam_rms_project_id: true,
+    }
   });
+  if (res.adam_rms_project_id) {
+    await AdamRMS.setProjectStatus(res.adam_rms_project_id, "cancelled");
+  }
 }
 
 export async function reinstateEvent(eventID: number) {
-  await prisma.event.update({
-    where: {
-      event_id: eventID,
-    },
-    data: {
-      is_cancelled: false,
-    },
-  });
+  // Watch out! Cancelling an event in AdamRMS releases its assets, so un-cancelling
+  // an event can cause a kit clash. We need to check this first.
+  // Do it inside a transaction with a SELECT FOR UPDATE.
+  return await prisma.$transaction(async $db => {
+    const events = await $db.$queryRaw<{ adam_rms_project_id: number | null; }[]>`
+      SELECT adam_rms_project_id FROM events WHERE event_id = ${eventID} FOR UPDATE`;
+    if (events.length === 0) {
+      throw new Error("Event not found");
+    }
+    const event = events[0];
+
+    if (event.adam_rms_project_id) {
+      const changed = await AdamRMS.setProjectStatus(event.adam_rms_project_id, "confirmed");
+      if (!changed) {
+        return { ok: false, error: "kit_clash" };
+      }
+    }
+
+    await $db.event.update({
+      where: {
+        event_id: eventID,
+      },
+      data: {
+        is_cancelled: false,
+      },
+    });
+    return { ok: true };
+  })
 }
 
 export async function deleteEvent(eventID: number, userID: number) {
diff --git a/lib/adamrms/index.ts b/lib/adamrms/index.ts
index ec021f71..ab0f0ed1 100644
--- a/lib/adamrms/index.ts
+++ b/lib/adamrms/index.ts
@@ -103,3 +103,30 @@ export async function newQuickProjectComment(
     text: comment,
   })) as {};
 }
+
+export async function setProjectStatus(projectID: number, status: "tentative" | "confirmed" | "cancelled") {
+  let statusIDStr;
+  switch (status) {
+    case "tentative":
+      statusIDStr = process.env.ADAMRMS_TENTATIVE_STATUS_ID;
+      break;
+    case "confirmed":
+      statusIDStr = process.env.ADAMRMS_CONFIRMED_STATUS_ID;
+      break;
+    case "cancelled":
+      statusIDStr = process.env.ADAMRMS_CANCELLED_STATUS_ID;
+      break;
+    default:
+      invariant(false, `Invalid project status ${status}`);;
+  }
+  invariant(statusIDStr, "Missing status ID for status " + status);
+  const statusID = parseInt(statusIDStr, 10);
+
+  // We still need to check for kit clashes - it's possible that changing a cancelled
+  // project to un-cancelled will cause a clash.
+  const res = await makeRequest("/projects/changeStatus.php", "POST", {
+    projects_id: projectID.toString(10),
+    projects_status: statusID.toString(10),
+  }) as { changed: boolean };
+  return res.changed;
+}