Section 9 of the Companies Ordinance (Cap. 622) sets the definition: a company is limited by guarantee if it has no share capital and the liability of its members is limited by the articles to the amount each undertakes to contribute to the assets of the company on a winding up. Guarantee companies form their own category under section 66, and the mandatory articles follow in Part 3. Section 81 requires the company name and section 83(1) a statement that the liability of members is limited. Section 84(2) is the clause no guarantee company can omit: the articles must state that each member undertakes to contribute a required amount, not exceeding a specified figure, if the company is wound up while that person is a member or within one year after ceasing to be one.
Objects are optional for most companies under section 82(2), but mandatory under section 82(1) for a company holding a licence under section 103, which lets the Registrar dispense with "Limited" for an association formed to promote commerce, art, science, religion, charity or another useful object, on the conditions set under section 104. Section 99 voids any provision giving a person a right to participate in divisible profits otherwise than as a member. Where registered articles are silent, the model articles for guarantee companies in Schedule 3 to the Companies (Model Articles) Notice (Cap. 622H) apply by default under section 80, which is why a bespoke set is worth registering.
Charitable status is decided elsewhere. Exemption under section 88 of the Inland Revenue Ordinance (Cap. 112) turns on the wording of the governing instrument, and the Inland Revenue Department guidance on the clauses expected in a charity's governing instrument sets out what the assessor looks for.