(a) Invalidity of lien without notice. The lien imposed by section 6321 is not valid against any purchaser (as defined in paragraph (f) of § 301.6323(h)—1), holder of a security interest (as defined in paragraph (a) of § 301.6323(h)—1), mechanic's lienor (as defined in paragraph (b) of § 301.6323(h)-1), or judgment lien creditor (as defined in paragraph (g) of § 301.6323(h)-1) until a notice of lien is filed in accordance with § 301.6323(f)-1). Except as provided by section 6323, if a person becomes a purchaser, holder of a security interest, mechanic's lienor, or judgment lien creditor after a notice of lien is filed in accordance with § 301.6323(f)-1, the interest acquired by such person is subject to the lien imposed by section 6321.

(b) Cross references. For provisions relating to the protection afforded a security interest arising after tax lien filing, which interest is covered by a commercial transactions financing agreement, real property construction or improvement financing agreement, or an obligatory disbursement agreement, see §§ 301.6323(c)-1, 301.6323(c)-2, and 301.6323(c)-3, respectively. For provisions relating to the protection afforded to a security interest coming into existence by virtue of disbursements, made before the 46th day after the date of tax lien filing, see § 301.6323(d)-1. For provisions relating to priority afforded to interest and certain other expenses with respect to a lien or security interest having priority over the lien imposed by section 6321, see § 301.6323(e)-1. For provisions relating to certain other interests arising after tax lien filing, see § 301.6323(b)-1.