Share transfers in a Pte Ltd run on two statutes working in tandem. The Companies Act 1967 governs the corporate mechanics, and the Stamp Duties Act 1929 governs the tax. Section 126 of the Companies Act 1967 requires a proper instrument of transfer before the company may register a transfer, and the same section sets the rule that surprises most first-timers: under section 126(3), a transfer of shares in a private company does not take effect until the electronic register of members is updated by the Registrar. Signing the instrument transfers nothing on its own. Title moves on registration, not on execution, a position that has held since 3 January 2016 and remains the law today.
The directors control the gate. Section 157A of the Companies Act 1967 confirms that the business of a company is managed by its directors, which is why a board resolution approving the transfer is normally required before lodgment, and why the constitution may give directors a discretion to refuse registration or impose pre-emption rights that force the seller to offer shares internally first. Where the company declines a transfer, section 128 sets out the notice of refusal obligations. You should read your own constitution before drafting anything, because a model constitution and a heavily negotiated one treat transfer restrictions very differently.
On the tax side, section 45 of the Stamp Duties Act 1929 imposes ad valorem duty on the instrument transferring the shares, payable to IRAS. The Inland Revenue Authority of Singapore explains the mechanics in its IRAS guidance on stamp duty for share transfers, and the duty is computed on a Working Sheet derived from the company's latest accounts. Electronic execution is generally valid under the Electronic Transactions Act 2010, which makes signing and circulating these documents online unproblematic for most private companies.