I get the following error when trying to write my field update value. How do I fix it?


Error: Formula result is data type (Boolean), incompatible with expected data type (Text).


NOT(ISNULL(Customer_ID__c)) && NOT(ISBLANK(Customer_Id__c))


Current Field Update Formula

  • What is the field value that you want to display from the formula?
    – Dave Humm
    Commented Apr 4, 2017 at 10:37
  • 1
    your formula field type is text so you must return a text if your condition matches.
    – Safiya PV
    Commented Apr 4, 2017 at 10:53
  • I want the phone Number field in INVOICE object to be automatically field when I place an id in Customers ID field which shoud be same as Customer ID in Customers object.
    – bob
    Commented Apr 4, 2017 at 11:13
  • Why do you want to populate the field? You can have it as a formula field Customer_Lookup_Field__r.Phone_Number_field__c
    – o-lexi
    Commented Apr 4, 2017 at 15:27

2 Answers 2


here is an example to update contact phone number when you assign the account to a contact.

Step1: create Workflow on contact.Add condition to execute the workflow. if account is not null. enter image description here

step 2: Update contact Phone as Account phone. enter image description here


As per Documentation,

Use ISBLANK instead of ISNULL in new formulas. ISBLANK has the same functionality as ISNULL, but also supports text fields. Salesforce will continue to support ISNULL, so you do not need to change any existing formulas.

So instead just use


This should work.


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