Embodiments of the present invention provide a novel method, system and computer program product for tracing die units during material transfer from, for example, one factory or lot to another (and efficiently maintaining correspondence between die data and an individual die during, e.g., a lot transfer process). One or more embodiments of the present invention are intended to improve the mechanism of die-level traceability by assigning individual die IDs to each die unit in, e.g., each lot, and associating a range of die IDs with a corresponding index string. When, for example, some dies are transferred from, e.g., a first lot to a second lot, the entire die information associated with the first lot is copied to the second lot, and a different index string is assigned to the second lot to indicate the actual dies or range of dies that have been transferred. The first lot's index string is then adjusted to indicate the dies remaining after the transfer.