Design is the easiest Shopify hire to get wrong expensively, because the output looks good either way. A store can be beautifully designed and convert worse than what it replaced, and you won't know for a quarter.
Decide which of the three jobs you're buying. Look, brand, or experience — the ranges above differ by an order of magnitude, and briefing "we need a redesign" invites the most expensive interpretation. If you're unsure, a brand and UX audit ($1,000-$4,000) will tell you which before you commit to a full project.
Ask for live Shopify stores, not portfolios. Concept work on Behance and Dribbble looks superb because nothing constrains it. Shipped Shopify stores prove the designer can work inside theme architecture, section and block limits, checkout restrictions and app UI compatibility. Ask for five live URLs from the last twelve months, ideally in your category.
Verify there's a UX process, not just a visual one. Reputable designers ship research, wireframes or prototypes before high-fidelity work. A proposal that jumps straight to mockups for anything beyond a light refresh produces design that photographs well and converts poorly. Ask specifically what discovery includes and what evidence informs layout decisions.
Check who implements it. A designer handing files to your developer is a different arrangement from a studio that builds what it designs. Both work, but the handover is where budgets overrun — unclear specs, missing states, and mobile behaviour nobody documented. Ask what the deliverable actually contains: Figma files, a design system, documented states, or just screens.
Fix revision rounds in the contract. "Unlimited revisions" sounds generous and reliably produces scope creep on both sides. Two or three defined rounds with a clear approval step protects everyone.