Update - I was attempting to do this while down at Inspire (remote connection). I tried it from work last night and it does work nicely across the site collection, just can't be configured via our Citrix environment.

I am trying to create an item in another site collection and get the following error when I input the URL -

The security on this site is high so I tried one of the regular site collections and got the same result.  I'm site collection on these areas.  I've tried from a list workflow and a site workflow.  It looks like you have accomplished this portion of the task.  What action are you using to do this?  I'd appreciate any help you can provide or being pointed to a resource.  I need to have this up and running in the near future.

What about exporting the list and importing it into your site? Would that work?

Seems like it would use lots of resources. We probably will need to send new items 500 times a year. So I'd have to put in a trigger to know which item was added.

I could create a list for the transfer on both ends once all of the validation is done. Yeah I could use that as a work around. When I import the list is it creating a new list every time? I'd have to build a site workflow to process on the other end. Does each instance create a new list id?

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Is there a way to update an item from one site collection to another, like the create an item in another site? Why is there a create and no update?

Yes, you can update the item in another site collection using Call Web Service action.

Use the URL of the other site collection: _vti_bin/lists.asmx and Update List item method. Then create the Web Service message, something like below:

<?xml version="1.0" encoding="utf-8"?>

<soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:m="http://schemas.microsoft.com/sharepoint/soap/">

  <soap:Header>

  </soap:Header>

  <soap:Body>

    <m:UpdateListItems>

      <m:listName>ListName</m:listName>

      <m:updates>

<Batch OnError='Continue' ListVersion='1'>

<Method ID="1" Cmd="Update">

      <Field Name="ID" >{ItemProperty:InternalPositionID}</Field>

      <Field Name="Status" >Closed</Field>

   </Method>

</Batch>

</m:updates>

    </m:UpdateListItems>

  </soap:Body>

</soap:Envelope>

This will update the field Status = Closed on the list ListName where ID= ItemProperty:InternalPositionID. You can use this method to update the list in another web application as well as long as you have update access. Hope it helps.