At the end of the Shmitta year, all outstanding loans are nullified as the Torah states
“that this is the manner of the release; to release the hand of every creditor from what he lent his friend; he shall not exact from his friend or his brother, because time of the release for the Lord has arrived”
This will take place at the end of this year’s Jewish calendar. By writing a document known as “Pruzbul” you assign the collection of the debts to a Beit Din (a Rabbinically-sanctioned court) which prevents the cancellation from occurring. The court then allows you to collect the debt in their stead.
The latest this can be done by is the day before Rosh Hashana, September 13, 2015. You can see examples of the document at the RCA and Star-K. The rabbi is available to administer a pruzbul for you. Contact him at (781) 322-5686 or at email@example.com.