Qitzur Shulchan Arukh – 180:7-9
Someone who lend his friend and made with him the condition that the seventh year would not retire [anything] of his, even so [this loan] is retired. But if he made a condition with him that this particular debt would not be retired, even if this was during the shemittah year, [the year] doesn’t retire it. Similarly if he wrote in the contract a language of a deposit [rather than a loan], it does not retire.
If someone lend his friend for some number of years and the time of collection arrives after the shemittah, it is not retired, since he had no way to collect it before hand.
Spmeone who gives his debt over to court and says to them, “You collect for me my debt”, is does not retire.
Understanding the last clause of se’if 7 requires understanding the difference between piqadon (deposit) and halva’ah (borrowing). A deposit is not for the second party’s usage, he is appointed over it to guard it. A bank despot, where the bank is privately owned by Jews would be halva’ah, not piqadon. The bank does have the right to invest my money, as long as I can reach it when I need it. Which we saw already when discussing interest.
The law in 180:9 is the basis of pruzbul.