Hong Kong incorporated companies are the most straightforward target. Serve at the registered office shown on the Companies Registry record and copy the letter to the director and to any contractual address for service. Run a company search first: it will tell you whether the debtor has changed name, moved office, or already faces a petition. If the balance sits above the statutory threshold and is undisputed, say plainly that a statutory demand under section 178(1)(a) will follow. That sentence does most of the work.
Sole proprietors and partnerships hold a business registration certificate but no separate legal personality, so the debt is the proprietor's personal debt. Address the letter to the individual by name, adding the trading style, and check the registration record for the principal place of business. Escalation runs through Cap. 6, with a statutory demand in Form 162 under the Bankruptcy Rules (Cap. 6A). Never serve Form 1A on a sole proprietor. The wrong instrument is fatal and the debtor will apply to set it aside with costs.
Individual guarantors need a separate letter, not a copy of the company demand. A guarantee is a distinct contract with its own limitation clock and its own notice mechanics, often requiring that the principal debtor be called on first. Read it before drafting, as you would read the repayment terms in a personal loan agreement between individuals.
Forum selection shapes the closing paragraph. Small balances belong in the Small Claims Tribunal under Cap. 338, mid-range commercial claims in the District Court under Cap. 336, and larger ones in the Court of First Instance, where an unarguable defence can be disposed of by summary judgment under Order 14. Name the court you will use, because a demand that identifies the correct forum reads as if a solicitor is already instructed. Related recovery documents sit in the business and incorporation section for Hong Kong and, for landlords, in the rent arrears demand letter for Hong Kong tenancies.