Short answer

• Shopee and Amazon.sg are the two platforms most commonly regarded as having the most reliable, buyer‑friendly return systems in Singapore right now — Shopee for fast local handling and free POPStation returns under its CASE commitment, and Amazon.sg for consistent 30‑day windows and seller rules that include prepaid or returnless solutions for international sellers. For fashion/apparel specifically, ZALORA is the most dependable option because of its clear 30‑day exchange/return rules and fashion‑focused processes. (straitstimes.com)

Why these three stand out (quick bullets)

• Shopee: signed an MoU with the Consumers Association of Singapore (CASE) to resolve refunds/returns quickly (Shopee committed to ~2½ working days) and to provide widespread free return points (POPStations), which materially improves reliability and turnaround for buyers. (straitstimes.com)
• Amazon.sg: enforces a consistent 30‑day style return window for many products and recently required international sellers to provide a Singapore return address, prepaid return labels, or offer returnless refunds — reducing stalled returns and ensuring timely refunds. (sellercentral.amazon.com)
• ZALORA: clear, category‑based return windows (most items 30 days; some categories 7 days), dedicated return flows for apparel, and published processing times — makes it the most reliable for clothes/shoes where fit/exchange is common. Note ZALORA also monitors high returners and may apply processing fees in some cases. (support-sg.ZALORA-ops.com)

How to pick the “most reliable” for your situation

• If you want fastest dispute resolution and many free local drop‑off points: Shopee. (straitstimes.com)
• If you want uniform seller accountability and options like prepaid/returnless refunds for cross‑border sellers: Amazon.sg. (sellercentral.amazon.com)
• If you’re buying fashion and need easy exchanges/size swaps: ZALORA. (support-sg.ZALORA-ops.com)

Practical tips to avoid problems

• Check the item’s return eligibility and time window (marketplace sellers sometimes have different rules). (support-sg.ZALORA-ops.com)
• Keep original tags/packaging and take photos or an unboxing video for high‑value items. (support-sg.ZALORA-ops.com)
• For international sellers, confirm whether the seller provides a local return address or prepaid label (this avoids long, expensive overseas returns). (sellercentral.amazon.com)

If you want, I can:

• Compare the return rules side‑by‑side (time windows, free return availability, exceptions) for the specific stores you care about, or
• Check the latest policy pages for any other Singapore retailers you’re considering (Courts, Best Denki, Challenger, Qoo10, etc.).