GS1 US recently stopped offering the 'One-Off' GLN and instead restructured its pricing so that companies who only needed a small number of GLNs could obtain a valid GS1 Global Company Prefix at a very reasonable price.
However, if your organization is dealing with CMO,3PL or other supply chain suppliers/partners which obtained their GLNs through the 'One-Off' subscription service then ensure you follow the rules below provided by GS1 Global:
One off GLNs are handled as though they have a 12-digit GCP.
“one-off” GLN: AI (414): 0312345678913
Extension: AI (254): none
implied 12-digit GCP: 031234567891
EPC Pure Identity URI: urn:epc:id:sgln:031234567891.
“one-off” GLN: AI (414): 4012345678918
Extension: AI (254): 4711ekW
implied 12-digit GCP: 401234567891
EPC Pure Identity URI: urn:epc:id:sgln:401234567891.