While you have the cash advance, you must take reasonable precautions to keep the funds safe. 

After the period covered by the cash advance, you must provide a record of the expenses made with the cash advance to the CPC Accounting unit.  This is required even if you spent the cash advance completely or exactly like you planned in your budget.

The manner of recordkeeping is up to you.  Pick a system that works for you.  You can simply keep receipts and statements or you can keep an accounting log along with your receipts. 

One of the most common mistakes is keeping partial receipts, partial logs, and partially overlapping receipts and logs.  Inconsistencies make the accounting very difficult.  Whatever method you use, be consistent using it.

If your research covers a substantial amount of time, organize your receipts and accounting regularly.  It is a daunting task to tackle weeks of receipts after you get back to Chapel Hill.