Here’s a polished and professional version of your sentence:
"While creating an account, the password field requires a combination of both uppercase and lowercase letters. The same validation rule should be applied on the password setup page as well."
Or, if you want it shorter for a bug/task description:
"Password setup page should follow the same validation rule as account creation — requiring both uppercase and lowercase letter combinations."
Let me know if you want this phrased for a Jira ticket or dev handoff!