There are occasions where legally a "demand" is exactly what you need; e.g. A "formal demand notice" is a specific type of notice that a debtor is required to p

There are occasions where legally a "demand" is exactly what you need; e.g. A "formal demand notice" is a specific type of notice that a debtor is required to pay up immediately (i.e. 7 or 14 days) before a creditor files for involuntary bankruptcy (i.e. to force you into bankruptcy). Having said that you should never say "I demand" or "I require", it is always used to reference a document, a signed contract, a law, etc.