You must have an adjustment to income for something like a student loan.
If you moved in April, then if the student loan interest is $1,500 for example, then 3/12 applies to time outside of DC. or $375 in my example. There is no hard fast rule on doing this, but in my example, I used 3 months in Texas. Just use a reasonable logical method.
Post a comment if this does not fully answer your question.
