Sealed radioactive sources are used all over the world for beneficial purposes in areas including medicine, industry, research and agriculture. These sources are usually managed safely and securely while in use. However, after they become disused, sealed sources remain hazardous and must continue to be managed safely and securely. For sources that cannot be re-purposed or recycled, disposal provides the only permanent, safe, secure and sustainable management solution. A fundamental principle is that safety has to be assessed consistent with a graded approach. This ensures that the level of effort applied in carrying out safety assessment is commensurate with the magnitude of the risks from the facility or activity. In accordance with the relevant IAEA safety standards, this publication describes how the graded approach can be applied to post-closure safety assessment for the disposal of disused sealed radioactive sources in boreholes. It is intended primarily for those involved in developing or regulating borehole disposal facilities for disused sealed radioactive sources.