I stand corrected. Aracer is right…..although admittedly pedantic. It is not legal tender. Apparently that generally “means FA difference” (paraphrasing) according to the BOE website:
Legal tender has, however, a very narrow technical meaning in relation to the settlement of debt. If a debtor pays in legal tender the exact amount he/she owes under the terms of a contract (and in accordance with its terms), or pays this amount into court, he/she has good defence in law if he/she is sued for non-payment of the debt.
In ordinary everyday transactions, the term “legal tender” in its purest sense need not govern a banknote’s acceptability in transactions.