Short answer: no stains, tears or structural damage, and any upholstered item needs a visible fire safety label (BS 5852) or a shop legally cannot sell it — no exceptions for condition.
Look for a label sewn into a seam, usually under a cushion or on the underside of the piece, stating it meets fire safety regulations. Without it, this isn't a shop being cautious — it's illegal for them to resell it. This catches out a lot of donors with older or handmade upholstered furniture that predates the label being sewn in.
Check the shops currently accepting furniture near you — fewer shops take furniture than clothing, so it's worth checking before you arrange transport. Need someone to help sort it or arrange collection? See local donation helpers.