{
   recordType: "revenueplan",
   id: "26905",
   values: {
      custrecordrsm_rev_plan_soure_client: {
         value: "3183",
         text: "Facebook Technologies, LLC"
      },
      recordnumber: "387",
      "custentity_jam3_exec_producer.customer": {
         value: "5539",
         text: "Greg Meltzer"
      },
      item: {
         value: "566",
         text: "Professional Services"
      },
      status: "Completed",
      custrecordrsm_rev_plan_cons_fore: {
         value: "299",
         text: "299"
      },
      "revenuearrangement.revenueElement": "Revenue Arrangement #185",
      custrecordjam_rev_rec_plan_so: "",
      "source.revenueElement": {
         value: "13402",
         text: "Sales Order #161"
      }
   }
}

I am getting this error :

INVALID_FLD_VALUE You have entered an Invalid Field Value 13402 for the following field: custrecordjam_rev_rec_plan_so

when trying to setValue in a custom field (list: transaction) on a revenue plan header. I am loading the revenue plan, then trying to setValue. Any ideas?

Are you able to set the field to that value in the UI?

Yes