Where a decision is taken to grant leave, documents will be returned in accordance with current processes. These processes act as a checklist to ensure that relevant documents are collected and returned in a timely manner.
Home Office officials have worked with Royal Mail to ensure the process to return documents is secure and timely.
Section 17 of the Asylum & Immigration (Treatment of Claimants etc) Act 2004 gives the power to retain documents, such as a passport, where the Secretary of State or an immigration officer suspects a migrant is liable to removal and the retention of the document may facilitate removal.
The 2004 Act does not allow for the indefinite retention of documents. Where a person is later granted leave, in whatever capacity, the document must be returned to the holder unless it is a forgery.
The Home Office guidance can be found at: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/640156/Retention-of-documents-v8.0ext.pdf