I returned to school on XX/XX/XXXX to student teach, which qualified me for a deferment on all of my remaining, subsidized loans. By late XXXX, the deferment was finally processed and applied to my account. During the time leading up to that, I was making full payments on my loans, and a portion of those payments went towards interest payments. This interest should not have been accruing, however, as the loans are all subsidized. Because I had been in another program ( that allowed deferment ) from the time of graduation to 20 days before I returned to a full time student status, my interest balance had previously been {$0.00}. In the payments that I made while my loans were in deferment, a total of {$45.00} of the money was applied towards interest. Because my loans were in deferment from XX/XX/XXXX-XX/XX/XXXX ( though they did n't show up on my account as being out of deferment until XX/XX/XXXX ), the total amount of interest that should have accrued would be ~ {$26.00}. When my loans came out of deferment, they said there was ~ {$15.00} of interest in the account, which added to my principal. I know this is wrong, as I already paid more into my interest than was due while the loans were in deferment. I do n't know where that other money that went towards interest went. There was also {$15.00} applied to interest on a payment I made on XX/XX/XXXX, when nothing was due because, according to their computer at the time, my loans were in deferment. I requested that they please apply the full payment I made towards my principal, but they said that it was going towards " outstanding interest ''. I have made two requests to see, in full, how my account 's total interest is being calculated out, and both times have resulted in them uploading a document to my account that shows payments made and total principal, but nothing at all about total interest or interst accrued. The second time I made the request, I explicitly requested a daily print off of all account activity from XX/XX/XXXX to present, with special attention paid to total interest accrued and total interest due at the time of each payment. They sent me the exact same statement of payments made the second time, still giving me no indication of how much interest they had calculated out for me, where my previous overpaid interest went, or how much was due at each payment. When I finally sat down ( with my mother, an accountant ) and tried to create a spreadsheet to keep track of their calculations and my payments, none of the numbers from their bills matched up to anything we calculated out. The calculations for total principal balance and account balance, in addition to what we calculated out for interest vs. their calculation for " outstanding interest '', all came out completely different from what was printed on the account statements sent to me. Anywhere from {$0.00} to {$100.00} different. I have sent a third request for information, but it is becoming apparent that there are a lot of computing and math errors that are being ignored as I try to gather information. As it is, based on the calculations I made, I had over paid around {$20.00} in interest by XX/XX/XXXX, and approximately {$100.00} that should have been applied to my principal does n't exist. ( The missing {$100.00} comes from a principal balance I calculated based on how much money I had paid up against the small amount of interest that should have been acquired. The calculation I made does n't match up with the one displayed on my account. ) But I have no way of confirming my calculations, as FedLoan Servicing is repeatedly not providing me with enough information on my account for me to be able to figure it all out. I should be able to see, clearly in front of me, exactly how every calculation is being made, but that 's not an option.