E-way bill validity rules set distance-based time limits with limited extensions and transporter update obligations under Rule 138. E-way bill validity is distance-indexed with an initial period for up to 200 km and additional days for each further slab; over-dimensional cargo and multimodal shipments involving sea have separate shorter slabs. The relevant date is the generation date and time, days run until the following midnight, and the Commissioner may notify extensions for specified goods. Transporters may extend validity in exceptional circumstances by updating Part B of FORM GST EWB-01, and limited post-expiry extension is permitted within a short prescribed window.