diff --git a/OPENAPI_DOC.yml b/OPENAPI_DOC.yml
index 3413ffec..2d29e73e 100644
--- a/OPENAPI_DOC.yml
+++ b/OPENAPI_DOC.yml
@@ -6481,38 +6481,22 @@ paths:
         will return a list of system_ids that are already booked during the specified
         time range
 
-        if system_ids is set, then it will only return booked systems from that list'
+        if system_id is set on the event, then it will only return booked systems
+        from that list'
       tags:
       - Events
       operationId: Events_clashing_assets
-      parameters:
-      - name: period_start
-        in: query
-        description: event period start as a unix epoch
-        example: "1661725146"
-        required: true
-        schema:
-          type: integer
-          format: Int64
-      - name: period_end
-        in: query
-        description: event period end as a unix epoch
-        example: "1661743123"
+      requestBody:
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/PlaceCalendar__Event'
         required: true
-        schema:
-          type: integer
-          format: Int64
-      - name: system_ids
-        in: query
-        description: comma separated list of system_ids to check for clashes
-        example: sys-1234,sys-5678
-        schema:
-          type: string
-          nullable: true
+      parameters:
       - name: return_available
         in: query
-        description: return available systems, this requires system_ids be set to
-          the full list
+        description: return available systems, this requires system_id be set on the
+          event
         example: "false"
         schema:
           type: boolean
diff --git a/spec/controllers/events_spec.cr b/spec/controllers/events_spec.cr
index c94b6d32..81797e79 100644
--- a/spec/controllers/events_spec.cr
+++ b/spec/controllers/events_spec.cr
@@ -1348,9 +1348,18 @@ describe Events, tags: ["event"] do
       EventMetadatasHelper.create_event(tenant.id, system_id: "sys-5678", event_start: event_start + 5, event_end: event_end + 5)
       EventMetadatasHelper.create_event(tenant.id, system_id: "sys-9999", event_start: event_end + 100, event_end: event_end + 200)
 
+      clashing_event_body = {
+        event_start: event_start,
+        event_end:   event_end,
+        attendees:   [] of String,
+        private:     false,
+        all_day:     false,
+      }.to_json
+
       response = client.post(
-        "#{EVENTS_BASE}/clashing-assets?period_start=#{event_start}&period_end=#{event_end}",
-        headers: headers
+        "#{EVENTS_BASE}/clashing-assets",
+        headers: headers,
+        body: clashing_event_body
       )
       response.status_code.should eq(200)
 
@@ -1361,7 +1370,7 @@ describe Events, tags: ["event"] do
       clashing.should_not contain("sys-9999")
     end
 
-    it "returns only clashing system_ids from provided list" do
+    it "returns only clashing system_ids from provided system_id" do
       tenant = get_tenant
       event_start = 10.minutes.from_now.to_unix
       event_end = 30.minutes.from_now.to_unix
@@ -1369,9 +1378,19 @@ describe Events, tags: ["event"] do
       EventMetadatasHelper.create_event(tenant.id, system_id: "sys-1234", event_start: event_start, event_end: event_end)
       EventMetadatasHelper.create_event(tenant.id, system_id: "sys-5678", event_start: event_start, event_end: event_end)
 
+      clashing_event_body = {
+        event_start: event_start,
+        event_end:   event_end,
+        system_id:   "sys-1234",
+        attendees:   [] of String,
+        private:     false,
+        all_day:     false,
+      }.to_json
+
       response = client.post(
-        "#{EVENTS_BASE}/clashing-assets?period_start=#{event_start}&period_end=#{event_end}&system_ids=sys-1234,sys-9999",
-        headers: headers
+        "#{EVENTS_BASE}/clashing-assets",
+        headers: headers,
+        body: clashing_event_body
       )
       response.status_code.should eq(200)
 
@@ -1388,16 +1407,23 @@ describe Events, tags: ["event"] do
 
       EventMetadatasHelper.create_event(tenant.id, system_id: "sys-1234", event_start: event_start, event_end: event_end)
 
+      clashing_event_body = {
+        event_start: event_start,
+        event_end:   event_end,
+        system_id:   "sys-1234",
+        attendees:   [] of String,
+        private:     false,
+        all_day:     false,
+      }.to_json
+
       response = client.post(
-        "#{EVENTS_BASE}/clashing-assets?period_start=#{event_start}&period_end=#{event_end}&system_ids=sys-1234,sys-5678,sys-9999&return_available=true",
-        headers: headers
+        "#{EVENTS_BASE}/clashing-assets?return_available=true",
+        headers: headers,
+        body: clashing_event_body
       )
       response.status_code.should eq(200)
 
       available = Array(String).from_json(response.body)
-      available.size.should eq(2)
-      available.should contain("sys-5678")
-      available.should contain("sys-9999")
       available.should_not contain("sys-1234")
     end
 
@@ -1408,9 +1434,18 @@ describe Events, tags: ["event"] do
 
       EventMetadatasHelper.create_event(tenant.id, system_id: "sys-1234", event_start: event_start, event_end: event_end)
 
+      clashing_event_body = {
+        event_start: event_start,
+        event_end:   event_end,
+        attendees:   [] of String,
+        private:     false,
+        all_day:     false,
+      }.to_json
+
       response = client.post(
-        "#{EVENTS_BASE}/clashing-assets?period_start=#{event_start}&period_end=#{event_end}&include_clash_time=true",
-        headers: headers
+        "#{EVENTS_BASE}/clashing-assets?include_clash_time=true",
+        headers: headers,
+        body: clashing_event_body
       )
       response.status_code.should eq(200)
 
@@ -1431,9 +1466,18 @@ describe Events, tags: ["event"] do
       cancelled_event.cancelled = true
       cancelled_event.save!
 
+      clashing_event_body = {
+        event_start: event_start,
+        event_end:   event_end,
+        attendees:   [] of String,
+        private:     false,
+        all_day:     false,
+      }.to_json
+
       response = client.post(
-        "#{EVENTS_BASE}/clashing-assets?period_start=#{event_start}&period_end=#{event_end}",
-        headers: headers
+        "#{EVENTS_BASE}/clashing-assets",
+        headers: headers,
+        body: clashing_event_body
       )
       response.status_code.should eq(200)
 
diff --git a/src/controllers/events.cr b/src/controllers/events.cr
index 0852a7fe..e6d87d56 100644
--- a/src/controllers/events.cr
+++ b/src/controllers/events.cr
@@ -1765,30 +1765,30 @@ class Events < Application
 
   # lists conflicting system_ids based on event time range
   # will return a list of system_ids that are already booked during the specified time range
-  # if system_ids is set, then it will only return booked systems from that list
-  @[AC::Route::POST("/clashing-assets")]
+  # if system_id is set on the event, then it will only return booked systems from that list
+  @[AC::Route::POST("/clashing-assets", body: :input_event)]
   def clashing_assets(
-    @[AC::Param::Info(name: "period_start", description: "event period start as a unix epoch", example: "1661725146")]
-    starting : Int64,
-    @[AC::Param::Info(name: "period_end", description: "event period end as a unix epoch", example: "1661743123")]
-    ending : Int64,
-    @[AC::Param::Info(description: "comma separated list of system_ids to check for clashes", example: "sys-1234,sys-5678")]
-    system_ids : String? = nil,
-    @[AC::Param::Info(description: "return available systems, this requires system_ids be set to the full list", example: "false")]
+    input_event : PlaceCalendar::Event,
+    @[AC::Param::Info(description: "return available systems, this requires system_id be set on the event", example: "false")]
     return_available : Bool = false,
     @[AC::Param::Info(description: "include the clash times, this is not compatible with return_available", example: "false")]
     include_clash_time : Bool = false,
   ) : Array(String) | Array(NamedTuple(system_id: String, event_start: Int64, event_end: Int64))
-    if return_available && system_ids.nil?
-      raise Error::ModelValidation.new([{field: "system_ids".as(String?), reason: "Missing system_ids"}], "error validating event data")
+    raise Error::BadRequest.new("event_start must be present") unless event_start = input_event.event_start
+    raise Error::BadRequest.new("event_end must be present") unless event_end = input_event.event_end
+
+    sys_id = input_event.system_id || input_event.system.try(&.id)
+
+    if return_available && sys_id.nil?
+      raise Error::ModelValidation.new([{field: nil.as(String?), reason: "Missing system_id"}], "error validating event data")
     end
 
     if return_available && include_clash_time
       raise AC::Route::Param::Error.new("include_clash_time and return_available cannot be used together")
     end
 
-    # Parse system_ids if provided
-    sys_ids = system_ids.try(&.split(',').map(&.strip).reject(&.empty?)) || [] of String
+    starting = event_start.to_unix
+    ending = event_end.to_unix
 
     # Query for clashing events
     query = EventMetadata
@@ -1796,24 +1796,24 @@ class Events < Application
       .where("event_end > ? AND event_start < ?", starting, ending)
       .where("cancelled = ? OR cancelled IS NULL", false)
 
-    # Filter by system_ids if provided
-    query = query.where({:system_id => sys_ids}) unless sys_ids.empty?
+    # Filter by system_id if provided
+    query = query.where({:system_id => sys_id}) if sys_id.try(&.presence)
 
     clashing_events = query.to_a
 
     if include_clash_time
       result = [] of NamedTuple(system_id: String, event_start: Int64, event_end: Int64)
-      clashing_events.each do |event|
-        if sys_id = event.system_id
-          result << {system_id: sys_id, event_start: event.event_start, event_end: event.event_end}
+      clashing_events.each do |evt|
+        if clashing_sys_id = evt.system_id
+          result << {system_id: clashing_sys_id, event_start: evt.event_start, event_end: evt.event_end}
         end
       end
       result
     else
-      clashing_system_ids = clashing_events.compact_map(&.system_id).uniq
+      clashing_system_ids = clashing_events.compact_map(&.system_id).uniq!
 
       if return_available
-        clashing_system_ids = sys_ids - clashing_system_ids
+        clashing_system_ids = [sys_id].compact - clashing_system_ids
       end
 
       clashing_system_ids