The CreateIRMark procedure in the HMRC Submission Helpers Codeunit is marked as OnPrem and can't be used in the cloud.

An overload procedure can be added that has a built in XMLDocument as a parameter that is converted to a .net XMLDocument and call the standard CreateIRMark procedure.

    procedure CreateIRMark(XMLDoc: XmlDocument; GovTalkNameSpace: Text; TaxNameSpace: Text): Text

    var

        XMLDocument: DotNet XmlDocument;

        XMLText: Text;

    begin

        XMLDoc.WriteTo(XMLText);

        XMLDocument := XMLDocument.XmlDocument;

        XMLDocument.LoadXml(XMLText);

        exit(CreateIRMark(XMLDocument, GovTalkNameSpace, TaxNameSpace));

    end;