i seriously dont undertsand whats wrong for (var fld in objUsageVal) {                 log.debug('objUsageVal[fld]==',objUsageVal[fld]); //objUsageVal[fld]== 07/29/2021           if(objUsageVal[fld])         {           recUsage.setValue({ fieldId: fld, value: objUsageVal[fld]});         } }

{
   type: "error.SuiteScriptError",
   name: "INVALID_FLD_VALUE",
   message: "Invalid date value (must be MM/DD/YYYY)",
   stack: [
      "anonymous(N/serverRecordService)",
     
   ],
   cause: {
      type: "internal error",
      code: "INVALID_FLD_VALUE",
      details: "Invalid date value (must be MM/DD/YYYY)",
      userEvent: null,
      stackTrace: [
         "anonymous(N/serverRecordService)",
         
         "anonymous(N/serverRecordService)"
      ],
      notifyOff: false
   },
   id: "",
   notifyOff: false,
   userFacing: false
}

whyyy?????

the error message is deceptive

var formattedDateString = format.format({
              value: parsedDateStringAsRawDateObject,
              type: format.Type.DATE
          });
  
  
      //else usageDateFinal = dtUsageDate;
      log.debug("usageDateFinal before set on record", formattedDateString);
  
      objUsageVal["usagedate"] = formattedDateString;
      // Customer, Item and Subscription Plan will be automatically sourced

this is the code just before that

is

objUsageVal[fld]

a string or a Date?

its a date

are you sure

should format.format again before setting?

the name

formattedDateString

suggests you thought it was a string

var parsedDateStringAsRawDateObject = format.parse({               value: usageDateFinal,               type: format.Type.DATE           });

format.format documents when it returns a strong and when it returns a Date

but still it is getting formatted as suggest

a formatted string is still not a Date

i dont understand bro

you will need to understand the difference between a string and a Date

i guess you are right

and need to be able to tell if

objUsageVal[fld]

is a string or Date

Why are you even using

format.format

? If you are using setValue, just pass it a date object. No need to format it.