The latest you can sit your SATs if your applying early is November; the latest for regular decision is January. However if you are applying for a school that requires SAT II subject tests, you will need to sit your SATs earlier as you cannot take SAT I and SAT IIs on the same day. I’m not sure what scholarships you are referring to specifically. But for financial aid and for scholarships like the robertsons, you will need to sit your SATs before as they are needed for you to be admitted in the first place. Always sit SATs ASAP. Saves you a lot of stress later.