Apply for / Apply to / Apply something to
UsageApply for names what is sought; apply to names the recipient or scope; apply something to names the rule, method or treatment being used.
Apply for
Use when
You name the leave, job, grant, licence, scheme or other thing being requested.
Example
“The officer will apply for leave through the HR system.”
Apply to
Use when
You name the organisation receiving an application, or the people, cases or situations covered by a rule.
Example
“The revised requirement applies to all vendors.”
Apply something to
Use when
You mean put a rule, method, test or treatment into effect for a particular case or object.
Example
“Apply the revised threshold to procurements initiated after 1 October.”
Quick check
apply leave, the policy applies for all officers, apply the agency for funding
Usage note
For an application, a person may apply to an organisation for something. In formal workplace writing, write apply for leave rather than apply leave.