336.Subsection (1) of section 157 sets out the circumstances in which an appeal against a certificate may be made and subsection (2) provides that no appeal may be made until the claim to which the compensation payment relates has finally been disposed of and the amounts set out in the certificate of NHS charges have been paid. Subsections (4) and (5) enable compensators to apply for the requirement for prior payment in subsection (2) to be waived, and allow the Secretary of State or the Scottish Ministers to grant such a waiver only where it appears to him or them that requiring payment would cause exceptional financial hardship. Subsection (6) provides compensators with a right of appeal against a waiver decision using the same mechanisms as for an appeal against a certificate. It is envisaged that the waiver would only be granted in truly exceptional cases, such as where the raising of money which might later fall to be refunded might, for example, put an individual’s home at risk or bankrupt a single-handed business.