Indemnity for tax withholding protects persons who deduct or pay tax on another's income from liability. Clause 518 establishes a statutory indemnity for any person who, under the Act, deducts, retains or pays tax in respect of income that belongs to another person, protecting such third-party deductors or payors against liability arising from those acts by ensuring they are indemnified for the deduction, retention or payment effected pursuant to the Act.