Justice WILLETT delivered the opinion of the Court.

Roark Amusement & Vending, L.P. brought this tax-refund suit against the Comptroller of Public Accounts, seeking to recoup sales taxes it paid on "plush toy" prizes used to stock its coin-operated amusement machines. The court of appeals held the toys were exempt from sales tax under the Tax Code's sale-for-resale exemption. We agree and affirm the court of appeals' judgment.

I. Factual and Procedural Background

The facts are undisputed, having been established below in a stipulation of facts or in uncontested affidavits. Roark owns and leases coin-operated amusement crane machines that are found in supermarkets, restaurants, and shopping malls throughout Texas. Customers aim to win plush toys by using a joystick to maneuver a mechanical claw to grab the toys and drop them into a prize chute. Successful customers keep the prizes, and eventually all the toys become property of customers in this manner (except for those lost, stolen, or damaged).

Roark sought a refund of the sales taxes it paid on the toys it purchased to stock its machines for the period October 1, 2000 through February 29, 2004.1 It argued that the toys were exempt under the sale-for-resale exemption discussed below. The Comptroller disputed that the exemption applied.

The trial court granted the Comptroller's motion for summary judgment and denied Roark's refund request. The court of appeals reversed, concluding the toys were exempt, and remanded the case to the trial court for a determination of the refund amount due Roark.2 We granted the Comptroller's petition for review.

II. Discussion

Our decision turns on the interplay of various Tax Code provisions found in chapter 151.

When construing a statute, our chief objective is effectuating the Legislature's intent, and ordinarily, the truest manifestation of what lawmakers intended is what they enacted.6 This voted-on language is what constitutes the law, and when a statute's words are unambiguous and yield but one interpretation, "the judge's inquiry is at an end."7 We give such statutes their plain meaning without resort to rules of construction or extrinsic aids.8 On the other hand, "[i]f a statute is vague or ambiguous, we defer to the agency's interpretation unless it is plainly erroneous or inconsistent with the language of the statute."9

We agree with Roark that under a plain-meaning review of the relevant statutes, it qualifies for a sales-tax exemption on the plush toys that fill its crane machines. The machines provide a taxable amusement service under sections 151.0028 and 151.0101, in that they provide for "amusement, entertainment, or recreation" under section 151.0028. The toys are subject to the sale-for-resale exemption because under section 151.006(a)(3), the toys are "tangible personal property" acquired by Roark "for the purpose of transferring" the toys "as an integral part of a taxable service." Indeed, the toys are more than integral to the machines' amusement service — they are indispensable. There would be no point (or profit) to the game — and thus no game — if customers had no chance of winning a toy. Roark contends in its principal brief, and the Comptroller does not dispute, that "[c]ustomers would not pay to play an empty machine (i.e., they would not pay to move a crane's claw around an empty glass case), nor would they pay to play if the machines contained toys that were impossible to retrieve."

The Comptroller makes two arguments that are incompatible with the statutory text, and thus unpersuasive.10

A. Do Roark's Crane Machines Provide a "Taxable Service"?

The Comptroller argues that the sale-for-resale exemption fails because the amusement service provided by Roark is not a "taxable service" under section 151.006(a)(3). That is, since section 151.335(a) exempts amusement services provided by coin-operated machines, the service here is not taxable. We disagree with this construction, and instead find persuasive the court of appeals' analysis of this issue.

Taxable service is a defined term under chapter 151. If a term is expressly defined by statute we must follow that definition.11 Section 151.0101 defines "taxable service" to include "amusement services," whether provided by coin-operated machines or otherwise. The fact that section 151.335(a) sets out an exemption for amusement services provided by coin-operated machines does not alter the fact that the machines provide a taxable service as defined in section 151.0101. Indeed, there would be no need to provide an exemption for this particular service if it were not a taxable service in the first instance. As noted above, under section 151.010, "taxable item" refers to "tangible personal property and taxable services." Section 151.301, the first provision of subchapter H, which sets out exemptions, provides: "If a taxable item is exempted from the taxes imposed by this chapter, the sale, storage, use, or other consumption of the item is not subject to the sales tax imposed by Section 151.051 of this code ..." (emphasis added). This section confirms that under chapter 151 an item exempt from taxation may nevertheless be included in the universe of taxable items.12 Taxable items in turn include taxable services, and taxable services include amusement services, under the provisions discussed above. Similarly, section 151.005 defines a "sale" or "purchase" to include "the performance of a taxable service ... or, in the case of an amusement service ... the use of a coin-operated machine" (emphasis added). Again, even though amusement services provided via coin-operated machines are later exempted in section 151.335(a), the definitional language of chapter 151 itself confirms that the performance of an amusement service through a coin-operated machine — the precise situation presented here — is a taxable service. Examining chapter 151 as a cohesive, integrated whole confirms that Roark's construction is the correct one.13

B. Is the Chance to Win an "Integral Part of a Taxable Service"?

Alternatively, in looking to language in section 151.006(a)(3), requiring that the transfer of toys be an "integral part" of the service provided, the Comptroller argues that the sale-for-resale exemption in section 151.006(a)(3) does not apply unless a toy is conveyed each and every time a customer plays the game. The Comptroller urges that section 151.302(b) imposes such a requirement by stating that tangible personal property is not considered resold unless the care, custody, and control of the property is "transferred to the purchaser of the service." We disagree. These provisions do not impose, either explicitly or implicitly, any such extra-statutory requirement, and we decline to engraft one — revising the statute under the guise of interpreting it.

We believe that in the area of tax law, like other areas of economic regulation, a plain-meaning determination should not disregard the economic realities underlying the transactions in issue.14 Here, the summary-judgment evidence shows that all the toys placed in Roark's machines eventually become customers' property, except for those lost, stolen, or damaged. Further, the economic reality of the game is such that customers simply would not part with their money but for the possibility of winning a toy. In this practical sense, under section 151.006(a)(3), the transfer of toys is "an integral part" of the amusement service offered by Roark's machines. The Comptroller acknowledged at oral argument that no one would play the game without the possibility of winning a toy. Nothing in section 151.302(b) suggests that every single customer must walk away with a toy. That provision requires that "care, custody, and control of the tangible personal property" be "transferred to the purchaser of the service." This transfer in fact occurs and is integral to the success of the game as an amusement service.

The Comptroller's argument that reference to "the purchaser" rather than a purchaser requires that the customer must always, inexorably win a toy simply puts too much weight on the commonest article of speech. The wording of the statute and the economic realities of the transaction do not require this "everyone's a winner" result. Indeed the game would lose all intrigue, and thus all profitability, if customers won each and every time. No profit-seeking businessperson would rationally offer such a sure thing. The game would cease to be a game, and thus cease to amuse, and thus cease altogether.

The Comptroller contends that her position is set out in Comptroller Rule 3.301(b)(2),15 which provides: "The operators of games, or other concessions, in which each participant does not receive some merchandise or prize, become the consumers of merchandise so used by them and are liable to the State of Texas for tax based on the sales price or use of the taxable items purchased for use by them." As explained in her principal brief, the Comptroller's position is that, under Rule 3.301(b)(2), "when each participant does not receive a prize, the game operator — or concessionaire — is not a retailer, but a consumer of the items it purchases to provide its service; such game operators are therefore not eligible to claim the resale exemption on purchases of toy prizes." Roark disputes that this Rule applies to its machines, describing it as outdated or alternatively invalid, and arguing that other rules apply instead, specifically Rules 3.301(c)(1) ("For an explanation of the taxability of an item purchased for use as a prize when the winning of the prizes depends upon chance or skill, see § 3.298(f)(1) of this title (relating to Amusement Services)."), 3.298(f)(1) ("Sellers of service may issue a resale certificate in lieu of tax to suppliers of tangible personal property only if care, custody, and control of the property is transferred to the client."), and 3.298(f)(2) ("A service will be considered an integral part of a taxable service if the service purchased is essential to the performance of the taxable service, and without which the taxable service could not be rendered.").16 The Comptroller disputes the applicability of these Rules to this case. Regardless of which Comptroller Rule applies, the Comptroller cannot through rulemaking impose taxes that are not due under the Tax Code; the question of statutory construction presented in this case ultimately is one left to the courts.

III. Conclusion

We affirm the court of appeals' judgment and remand the case to the trial court for further proceedings consistent with this opinion.