What happens to warranty claims on work the trades business did before I bought it?

Responsibility for warranty claims on pre-sale work depends on what the purchase agreement says, layered on top of what the deal structure implies by default. In a share sale, the corporation that did the original work continues to exist and generally remains responsible for its own warranties, since the buyer is simply acquiring that same corporation going forward — meaning the buyer effectively steps into responsibility for honouring those warranties as the new owner of that entity. In an asset sale, warranty obligations don't automatically follow the assets unless the purchase agreement specifically has the buyer assume them; left unaddressed, that responsibility can stay with the seller, who may or may not still be around or solvent enough to honour it.

Because customers generally don't distinguish between "the business" and "the legal entity," a buyer who wants to protect the business's reputation often ends up handling warranty claims on past work even where they aren't strictly obligated to, which is why this needs to be a deliberate decision in the purchase agreement rather than an assumption. Clear allocation of responsibility, backed by an indemnity or holdback for a defined period, protects both sides from disputes over who pays for a callback on old work.