Yes, an ISF can be processed without an ISF-D Single Transaction Bond if the importer does not have a C1 Continuous Bond. However, a bond is still required in order to file an ISF. If the importer does not have a C1 Continuous Bond, they can use a single transaction bond (CBP Form 301) or a continuous bond (CBP Form 301A) as an ISF bond. Alternatively, the importer can also allow their agent or customs broker to use their bond to cover the ISF filing.