The short answer
For most private sales — furniture, electronics, equipment, even most vehicle sales — no notary is required. A bill of sale becomes binding when it contains the essential elements (buyer, seller, property description, price, date) and both parties sign it.
When notarization is required
A small number of states require a notarized bill of sale specifically for motor vehicle transfers, and requirements occasionally change. The reliable move is a two-minute check of your state DMV's title-transfer page before you meet the buyer. If notarization is required, sign in front of the notary — not before.
Why you might notarize anyway
Even where it's optional, notarization adds real protection on higher-value sales: it establishes the identity of the signers and the date of signing. If a dispute ever lands in small claims court, a notarized document is very hard to argue with. For a $200 dresser, skip it; for a $15,000 truck, consider it.
How to add a notary block
PlainBill's generator includes an optional notary acknowledgment section — toggle 'Include notary acknowledgment block' and the signature area for the notary is added to your document automatically. Bring the unsigned document to the notary and sign there.