Warranty rules

Every registration gets the most specific rule that applies:

Product exception (one product), else
Collection rule (the top one in the list if the product is in several collections), else
Default warranty (Settings → General).

Variants share their product's rule.

What a rule sets

Warranty: Products have a warranty, or no warranty (registration without a warranty).
Length in months.
What the warranty covers (optional): shown on the customer's card.
How customers identify the product: SKU or barcode, SKU only, Barcode only or Serial number.
With Serial number, Serial number check: Any serial number, Must match a format (with Serial number format) or Must be on my imported list (see Serial numbers).

Settings → Rules:

Add collection rule: pick a collection, set the terms, Save rule. Move rules up and down: the top one wins when a product is in more than one collection.
Add product exception: pick a product, set the terms, Save rule.

Up to 100 rules per store.

Test a product shows which rule a product gets and why. Use it after changing the order of collection rules.

A store sells kitchen tools, lamps and stoves:

Default: 24 months, SKU or barcode.
Collection "Lighting": 36 months, Serial number, format HL-#####.
Product exception "Basecamp Stove": 60 months, Serial number, Must be on my imported list.