My loans have been sold to many different lenders and serviced by many different companies over the last 8 years.  Each servicer seems to have different rules about how to apply double-payments/advance-payments (is this permissible?).  During the last sale of my loan (and change in servicer), some of my extra payments from 2012 seem to have disappeared.  The new lender will only give me historical information dating to the date they acquired the loan and the old servicer’s website is no longer active.

How can I get a copy of the “money trail” = i.e. where all my payments went (it just doesn’t make sense to me that neither my payment amount, nor the terms of my repayment have changed in 8 years, despite having paid nearly twice as much as my payment due for 12 months)?  Also, shouldn’t the date of the final payment have accelerated due to the extra payments?

I’m sorry you are dealing with this situation.  A couple of things: for federal student loans, “over"payments are applied according to specific rules.  Depending on the loan “status”, payment is typically directed first to collection cost and fees, if any, then to unpaid interest, finally to principal.  Servicers may postpone the next due date if a payment covers more than one monthly payment, but a borrower may request that the due date not be postponed in writing.

As far as getting records, always ask in writing, phone requests don’t cut it.  If you don’t get what you ask for, consider complaining to the federal student loan ombudsman and/or the Consumer Financial Protection Bureau for private loans.

Check out this helpful sample letter to loan servicers: http://files.consumerfinance.gov/f/201310_cfpb_consumer_advisory_student_loan_repayment.pdf