Are crisps ultra-processed?

This is the one people expect to be obvious and it is not. Ready salted crisps made from sliced potato, oil and salt are group 3. Three ingredients, all of which a kitchen has.

Flavoured is a different answer

Almost every flavoured crisp is group 4, because the flavour is delivered by flavourings, flavour enhancers and often colourings. Cheese and onion contains neither cheese nor onion in the sense you would mean at home.

• Potatoes, sunflower oil, salt: group 3.
• Flavouring, flavour enhancer, monosodium glutamate, colour, dextrose: group 4.
• Anything made from potato flakes or reconstituted potato rather than sliced potato is group 4 by construction.
• Most extruded or puffed snacks are group 4 for the same reason.

Why this one matters for a receipt

Crisps are the item most people assume drives their ultra-processed share, and on a real receipt they usually do not. They are cheap and they are a small number of lines. The larger share is generally in staples bought weekly: bread, sauces, ready meals and anything reduced-fat. That gap between what people expect and what the receipt says is the whole reason the itemised breakdown is worth having.

Working this out from a receipt is harder than from a packet, because a till prints about twenty characters of product name and no ingredients list. That is the problem Bagged exists to solve, and how a receipt is structured explains why it is the hard part.