Can the seller change their mind on closing day after everything else is already signed?

Once the purchase agreement itself is signed and unconditional, a seller generally can't simply refuse to close because they've changed their mind — doing so is a breach of a binding contract, not a right the seller retains. The signed agreement is what obligates the seller to actually complete the sale on the agreed terms, and "changing my mind" isn't, on its own, a recognized way out of that obligation.

A seller who refuses to close on that basis exposes themselves to the buyer's remedies for breach, which can include a damages claim for the buyer's losses from the deal falling through, and in some circumstances a claim to force the sale through rather than simply accepting money instead. If the agreement is still conditional — some condition genuinely hasn't been met — the analysis is different, since an unsatisfied condition can give either side a legitimate way to step back. The key question is always whether there's still an unmet condition or right to terminate, not simply whether the seller has had second thoughts.