On Monday of Parshat Ki Teitzei (Sept. 8), HaGaon Rav Asher Zelig Weiss, ShLiT"A gave a shiur on Shmittas Kesafim. His main discussion was about how a pruzbal works - i.e., what exactly is one giving over to Bet Din and why does that permit the creditor to collect his debt. Toward the end of the Halachic portion, he discussed what types of debts are affected by Shmittas Kesafim if there is no pruzbal and, therefore, require a pruzbal.
One of the more interesting issues was if one is holding a check that has not been deposited or cleared. He said for checks that are post-dated for after Rosh Hashannah, there is no need for a pruzbal because Shmittah does not affect debts whose payment time has not arrived. For current checks, he quoted many contemporary poskim who maintain that since checks are passed from person to person (even third party) and are accepted as payment, they are like monetary bills and there is no need for a pruzbal.
He disagrees with this psak and holds that any check that has not yet cleared the bank is an uncollected debt and requires a pruzbal. He qualified it by saying that the State of Israel is a world leader in numerous categories. One of these is that the State of Israel is #1 in the world in the volume of returned checks. He claims that since, if a check (here in Israel) has not yet cleared the bank, there is a fairly reasonable likelihood that it isn't going to clear the bank, then any check must be looked upon as an uncollected debt.