Taxability of guarantees: personal guarantees may have zero taxable value; corporate guarantees are valued under related-party rules. Personal guarantees by directors for company borrowings constitute a supply of service between related persons and are valued at open market value; where regulatory mandates bar any consideration the open market value may be zero and taxable value nil, except where remuneration is in fact paid. Corporate guarantees by related companies or by a holding company for a subsidiary are treated as supplies between related persons and must be valued under the amended related-party valuation provision, which applies regardless of input tax credit availability; that amended provision does not apply to personal guarantees.