A vendor unwilling or unable to provide GST invoicing on a bulk order is the clearest red flag — this isn't a minor administrative detail, and its absence usually signals broader informality in how the vendor runs its business.
Vague or shifting delivery timelines are the second major warning sign. A vendor who won't commit to a specific delivery window in writing, or whose estimate changes significantly between initial quote and order confirmation, is a real risk for any date-sensitive gifting occasion.
Be cautious of pricing that seems significantly below market for the stated product and quantity — this usually means either a different (lower-spec) product than discussed, or a vendor cutting corners somewhere that will surface later in the order.
Finally, check whether the vendor can show evidence of having actually fulfilled orders at your required scale — a vendor whose largest prior order is a fraction of your planned volume carries real execution risk, however confident they sound in the sales conversation.