Petitioner seeks review of a decision by an administrative law judge (ALJ) of the Department of Consumer and Regulatory Affairs. The only contention made by petitioner in this court is that the ALJ applied an erroneous definition of the word “willful” in concluding that he had willfully *368 breached certain warranties. We reject his contention and affirm the decision of the AU. |

In 1979 petitioner sold a house to Garrett and Donna Cpitwood. A clause in the contract of sale provided that “[t]he premises, appliances and certain systems shall be warranted as stated in the ‘Residential Real Property Transfer Excise [Tax] Act of 1978/ ” comiponly known as the Speculator’s Tax Act. Within the applicable warranty periods, several problems developed with the houée. When petitioner failed to alleviate them, the Chitwoods filed a complaint with thje Office of Consumer Protection, which then began an administrative proceeding against petitioner. After an ev-identiary heating, an AU found that petitioner had willfully breached the statutory warranties with respect to a malfunctioning refrigerator, a sagging floor, a fuel oil tank whose bpttom had fallen out, and the presence of ¡water in the furnace room. The AU foupd that petitioner had knowledge of each j)f these defects in the property. Because there was substantial evidence to support these findings, we cannot disturb them. See D.C.Code § 1-1510(a)(3)(E) (11981).

Petitioiier contends that, absent a finding of bajd faith or moral culpability, the AU erred in concluding that he had willfully breajched the warranties. 1 This court has repeatedly held that it will defer to an administrative agency’s interpretation of a statute with whose enforcement it is charged, so! long as that interpretation is reasonable arjd not inconsistent with the statute itself. McMullen v. Police & Firefighters Retirement & Relief Board, 465 A.2d 364, 366 (D.C. 1983); Totz v. District of Columbia Rental Accommodations Commission, 412 A.2d 44, 46 (D.C. 1980). The question for us to decide here, then, is whether the jAU’s interpretation of the statutory language was reasonable. We hold that it was.

The word “willfully” can mean different things in different contexts. See, e.g., Spies v. United States, 317 U.S. 492, 63 S.Ct. 364, 87 L.Ed. 418 (1943) (“willfully” in two different but related sections of the Internal Revenue Code construed two different ways). Petitioner contends that, as used in the Speculator’s Tax Act, the word necessarily includes an element of bad faith or moral culpability. We cannot agree. Even in the criminal law, willfulness is seldom defined so broadly.

It is only in very few criminal cases that “willful” means “done with a bad purpose.” Generally, it means “no more than that the person charged with the duty knows what he is doing. It does not mean that, in addition, he must suppose that he is breaking the law.”

Townsend v. United States, 68 App.D.C. 223, 229, 95 F.2d 352, 358, cert. denied, 303 U.S. 664, 58 S.Ct. 830, 82 L.Ed. 1121 (1938), quoting from American Surety Co. v. Sullivan, 7 F.2d 605, 606 (2d Cir. 1925) (Learned Hand, J.). In civil or administrative proceedings, willful conduct is most often defined simply as that which is intentional, rather than inadvertent or accidental. 2 See United States v. Murdock, 290 U.S. 389, 394, 54 S.Ct. 223, 225, 78 L.Ed. 381 (1933). That is the sense in which the AU in this case found that petitioner had willfully breached the warranties, citing such cases as Monday v. United States, 421 F.2d 1210, 1215 (7th Cir.), cert. denied, 400 U.S. 821, 91 S.Ct. 38, 27 L.Ed.2d 48 (1970). This is consistent with our own decisions in Bohannon v. District of Columbia Department of Motor Vehicles, 288 A.2d 672, 674-675 (D.C. 1972), and Sherman v. Commission on Licensure to Practice the Healing Art, 407 A.2d 595, 599-600 (D.C. 1979). See also, e.g., Gear- *369 hart & Otis, Inc. v. SEC, 121 U.S.App.D.C. 186, 190-191, 348 F.2d 798, 802-803 (1965).

Petitioner offers no authority for his claim that a willful breach cannot be established without a showing of bad faith or moral culpability. Since the AU’s construction of the term is neither unreasonable nor contrary to the purpose of the statute, we accept it and reject petitioner’s arguments. The decision of the Department of Consumer and Regulatory Affairs is therefore

Affirmed. 3