Dr. Vito Cardone, the plaintiff, entered into an agreement (Agreement) with MedTeam Management Services, Inc. (MedTeam), on February 1, 1989, to provide professional medical and management services at the Fertility Center (Fertility Center or Center) of the Boston Regional Medical Center (BRMC). The Agreement was to run until September, 1994. Disagreements arose, however, over how the plaintiff’s compensation was calculated, and in October, 1993, the Agreement was terminated.

Dr. Cardone filed a scattershot twenty-three count complaint against numerous defendants alleging various claims for damages arising out of the Agreement.2 The defendants moved for partial summary judgment.3 The plaintiff now appeals from the summary judgment entered for BRMC as a separate and final *181judgment on so much of the plaintiff’s breach of contract claim (count II) as alleges that BRMC made improper adjustments to revenue, and count VI, alleging that BRMC tortiously interfered with the Agreement between the plaintiff and MedTeam.4 The plaintiff also appeals the denial of his motion to compel production of confidential Fertility Center records relating to patient services and billing.

The Agreement provided that the plaintiff’s compensation was based on two elements: (1) payment for the patient care services he rendered, and (2) payment for the administrative services he provided as director of the Center. This dispute specifically concerns the second element, the “administrative employment compensation.” According to the Agreement between Dr. Cardone and MedTeam, he was to receive as “administrative employment compensation” annually, “the lesser of seventy percent (70%) of the Center’s net revenues . . . or $750,000.”5 It was “payable ninety (90) days after the end of [MedTeam’s] fiscal year.”

The Agreement, which the defendants drafted, provided that *182MedTeam was to calculate the net revenue of the Center “based upon the following items of revenue and expense and in accordance with generally accepted accounting principles.” Revenue was to “include all collected revenues for management fees received by [MedTeam] arising out of services rendered in the Center to the Center’s patients.”6 Expense items were to “include both operating and capital costs (including marketing expenses, salaries, benefits, supplies, rental charges, depreciation and interest).”

Also in place was a management agreement between MedTeam and BRMC. The management agreement provided that MedTeam would manage the Fertility Center on behalf of BRMC. “As compensation for its management services under [the management] agreement, [BRMC] agrees to pay to MedTeam a fee equal to the Center’s gross collections for services performed in the Center, .... after deduction of [BRMC’s] monthly costs of renting the facilities used by the Center and of services, supplies and materials provided by [BRMC] to patients treated at the Center, which amounts shall be retained by [BRMC].” According to BRMC, this fee was the “collected revenues for management fees” referred to in the Agreement between Dr. Cardone and MedTeam.

Dr. Cardone argues that he was not fully compensated under the terms of his Agreement on account of three adjustments BRMC made to “collected revenues for management fees”; these adjustments are not expressly described in either the Agreement or in the management agreement between MedTeam and BRMC.7

First, a deduction was made to reflect what has been referred to as the “Blue Cross contractual allowance” or the “Blue *183Cross settlement.” Each year, Blue Cross only paid BRMC a percentage of the face value of BRMC’s total charges. According to the affidavit of Russell Wetherell, an officer of both BRMC and MedTeam, “[t]he process worked this way. Blue Cross would pay [BRMC] on an interim basis, usually in the range of about 93% of the face amount of its charges. At the end of a given year, however, Blue Cross and [BRMC] would then perform a ‘settlement,’ in which total charges for the year were subjected to a complicated formula,” which usually resulted in a percentage recovery below 93%. Final resolution of the settlement might not be completed until “some times, much much later after the end of the year,” and it would come in the form of a bill from Blue Cross.

The second adjustment was a deduction for the uncompensated care pool, a share of which each hospital in Massachusetts is responsible. According to Wetherell, “[a]t the end of each year, the Commonwealth would add up the entire cost of free care at all Massachusetts hospitals, and then express the cost as a percentage of total hospital revenues. Each hospital then had to compare its actual percentage of free care to this ideal percentage,” and if its percentage was lower (i.e., if its percentage was 10% and the Commonwealth’s percentage was 12%), it would then have to contribute the percentage difference of its revenues (i.e., 2%) to the uncompensated care pool. The working out of this charge-back could take years. The plaintiff claims that the Fertility Center did not serve indigent patients. The record also does not explain BRMC’s methodology for allocating its uncompensated care bills to the Fertility Center.8

The third adjustment reflected revenues set aside by BRMC, known as “deferred revenue,” to account for a “charge cap” imposed by the Commonwealth of Massachusetts. According to Wetherell, “the charge cap was a consequence of the tight reimbursement controls, and relatively low reimbursement levels, of government programs such as Medicare and Medicaid. *184The Commonwealth’s concern was that hospitals might try to make up what they perceived as shortfalls in reimbursement from government programs by increasing the rates that they charged to private payers such as health insurers and patients who paid their own bills. ... In order to make sure that didn’t happen, the Commonwealth annually calculated the amount of ‘private’ revenue that it thought each Hospital should earn in that year” and established a “charge cap.” According to Wetherell, “[p]rivate revenues that exceeded [that] cap were ... eventually . . . returned to the Commonwealth.” The charge cap was discontinued by legislation in 1991, but it took several years for the settlements to work out. Any surpluses were paid into the uncompensated care pool. The record does not explain BRMC’s methodology for allocating these costs to the Fertility Center.

Dr. Cardone asserts that the three adjustments were not discussed between or contemplated by the parties during the negotiation, execution, or operation of the Agreement.9 An earlier unsigned version of exhibit C to the Agreement, prepared by the defendants, described revenue as including “all charges, net of contractual allowances, bad debt and free care.” Why this language was replaced with the phrase “collected revenues for management fees” is unclear from the record. The three adjustments discussed above were also not made during the first two years the plaintiff’s Agreement with MedTeam was in effect.10 Beginning in 1991, Dr. Cardone requested, but did not receive from MedTeam, an accounting of the manner in which net revenue was calculated. Dr. Cardone objected, through his attomey, to these adjustments, which substantially reduced his earnings, and sought payment of the monies he alleged he was owed under the Agreement. According to his answers to interrogatories, the plaintiff was substantially undercompensated on account of these adjustments. Dr. Cardone attributes a direct loss of approximately $1,914,206 to the allegedly unauthorized *185adjustments from 1991 to 1993.11

Finally, as represented in his answers to interrogatories, the plaintiffs experts were expected to testify that the Agreement, when read as a whole, contemplated cash basis accounting, and that the reference to “generally accepted accounting principles” was only meant to “evoke the habitual use of prudent and widely recognized procedures in the conduct of financial affairs,” not “the technical definition of the term as used by specialists . . . that expressly excludes cash accounting.”12

In his memorandum of decision on the defendants’ motion for partial summary judgment, the Superior Court judge described the contract as follows: “At first glance, the [Agreement] seems clear as to the billing and administrative fee. Upon further examination, however, it is at best ambiguous; at worst, a hodgepodge of language designed to meet either party’s needs at any time.” He therefore denied summary judgment on breach of contract claims involving MedTeam’s 7% billing and administrative fee.13 He nevertheless allowed summary judgment on so much of the breach of contract claim against both MedTeam (Count I)14 and BRMC (Count II) as concerned the adjustments to revenue. He did so because the Agreement calculated net revenues according to “generally accepted accounting principles” (GAAP), and the Blue Cross settlement was made according to GAAP, as elucidated by the American Institute of Certified Public Accountants Audit and Accounting Guide, Health Care Organizations, and “[t]he remaining two *186adjustments were . . . based on advice from defendants’ auditors.” He also allowed summary judgment on the tortious interference with contract claims against both Perez (Count IX) and BRMC (Count VI), even though summary judgment was only sought against Perez.

Discussion. 1. Summary judgment. “If a contract. . . is unambiguous, its interpretation is a question of law that is appropriate for a judge to decide on summary judgment. . . . Where, however, the contract. . . has terms that are ambiguous, uncertain, or equivocal in meaning,” the intent of the parties may depend on disputed facts requiring a trial. Seaco Ins. Co. v. Barbosa, 435 Mass. 772, 779 (2002). See Affiliated FM Ins. Co. v. Constitution Reinsurance Corp., 416 Mass. 839, 845-846 (1994) (reversing allowance of summary judgment where contract language was ambiguous and evidence of trade usage, an undeveloped question of fact, was required to interpret contract); Citation Ins. Co. v. Gomez, 426 Mass. 379, 381 (1998) (term is ambiguous “if it is susceptible of more than one meaning and reasonably intelligent persons would differ as to which meaning is the proper one”).

a. Adjustments to revenue. The Agreement language regarding the treatment of the adjustments is ambiguous. The Agreement does not expressly address any of the three adjustments. Nor does the management agreement between MedTeam and BRMC. The definition of “collected revenues for management fees” is also too general, without a further explanation that is not provided, to be read as unambiguously excluding or including the three complicated adjustments. This lack of definition is particularly problematic as the adjustments were not even specific to the Fertility Center, but rather were imposed on BRMC as a whole, which then allocated the costs of the adjustments to the Fertility Center based on a methodology that is not explained in the Agreement or elsewhere in the record.15 The expenses and deductions allowed in both the Agreement and the *187management agreement between MedTeam and BRMC are also focused on items such as the cost of renting the Fertility Center space or the “services, supplies and materials provided by [BRMC] to patients treated at the Center,” not BRMC-wide adjustments. The remainder of the Agreement, which was drafted by the defendants, does not resolve the uncertainties.16

The extrinsic evidence in the record does not resolve the ambiguity. The plaintiff has submitted evidence that the three adjustments were never addressed during the negotiation of the Agreement. Earlier drafts of the Agreement referenced the Blue Cross contract allowance, and possibly the uncompensated care adjustment, but that language was dropped from the Agreement for unexplained reasons. For the first two years of the Agreement, no adjustments were made by the defendants. See Restatement (Second) of Contracts § 202 comment g (1981) (“The parties to an agreement know best what they meant, and their action under it is often the strongest evidence of their meaning”). Once the defendants made the adjustments in the third year, the plaintiff objected and demanded an accounting.

BRMC contends that the language in the Agreement providing that the calculation of “net revenue” will be done “in accordance with generally accepted accounting principles” compels recognition of the three adjustments. However, according to the plaintiff’s answers to interrogatories, he was prepared to offer expert witnesses with specialized knowledge in the areas of health care and tax accounting to dispute this contention. Suffice it to say that the accounting practices alluded to in the Agreement are uncertain and disputed on this record and will apparently require expert testimony. This was *188not a routine, mechanical, mathematical exercise. See generally Pittsburgh Coke & Chem. Co. v. Bollo, 560 F.2d 1089, 1092 (2d Cir. 1977) (“The term ‘generally accepted accounting principles’ . . . should not be interpreted in vacuo but only in relation to the particular type of business involved” and company’s own operation); A.P.N. Holdings Corp. v. Hart, 615 F. Supp. 1465, 1476 (S.D.N.Y. 1985) (“As in many of the matters discussed herein, the dispute over the accounting treatment... is, at bottom, one of opinion”). The solitary, passing reference to “generally accepted accounting principles” in the Agreement does not resolve the contractual question regarding the authorization of the three disputed adjustments in this particular contract.17

In sum, the determination whether “collected revenues for management fees” and the other ambiguous contract provisions at issue allow or disallow the three adjustments depends on undeveloped or disputed evidence regarding (1) the bargaining history of the parties; (2) the cost allocation methodology of BRMC and perhaps other hospitals similarly situated; and (3) generally accepted accounting principles and practices in the health care industry.

b. Tortious interference. The Superior Court judge also allowed summary judgment on Count VI of the complaint entitled “Malicious Interference with Contract — Cardone v. [BRMC].” *189Dr. Cardone contends that the Superior Court erred because BRMC had not moved for summary judgment on this count, thereby depriving him of notice and an opportunity to respond. Even if the court could act sua sponte, Dr. Cardone continues, summary judgment was inappropriate. The plaintiff essentially argues that BRMC made the disputed adjustments, knowing them to be inappropriate, in order to address its own financial difficulties. He also contends that BRMC interfered with his Agreement so that it could remove him and take for itself the profitable Fertility Center and its outstanding accounts receivable.

We conclude that summary judgment should not have been granted on this count. We have instructed judges to provide a fair opportunity for response before allowing a motion for summary judgment on counts where summary judgment has not been requested. Gamache v. Mayor of N. Adams, 17 Mass. App. Ct. 291, 295 (1983) (“In the circumstances we assume that the judge had the power, sua sponte, to enter full summary judgment [on a motion for partial summary judgment], provided that the parties had sufficient notice of his intention to do so, opportunity to submit affidavits, and a right to be heard on the matter”). See Quincy v. Massachusetts Water Resources Authy., 421 Mass. 463, 471 (1995); Monaco v. Lombard Bros., Inc., 24 Mass. App. Ct. 941, 941-942 (1987) (reversing judgment where judge granted motion for summary judgment on ground not raised by either party, without giving parties opportunity to address question). The record, albeit incomplete, raises questions about whether appropriate procedures were followed here. Furthermore, there are numerous facts in dispute regarding the Agreement, the course of extensive dealings between the different parties, and their motivations. Also, given the overlapping responsibilities of the different actors, including Perez, who was the president of MedTeam as well as the president and chief executive officer of BRMC, a trial will be necessary to resolve in which capacity various people were acting, and for whose benefit, when they made certain decisions.

In deciding that summary judgment was/not appropriate, we nonetheless recognize that the standard Tor proving tortious interference against [BRMC] is a high one. “Claims of *190intentional interference with contractual or advantageous relations require a showing that the defendant knowingly and for an improper purpose or by improper means induced a party to breach a contract. . . , resulting in damage.” Buster v. George W. Moore, Inc., 438 Mass. 635, 652 (2003). See United Truck Leasing Corp. v. Geltman, 406 Mass. 811, 812 (1990). Furthermore, as we stated in Williams v. B & K Med. Sys., Inc., 49 Mass. App. Ct. 563, 576 (2000), “related companies are allowed considerable latitude to interfere in the contractual relations of each other.” Nonetheless, it is premature to conclude that the plaintiff will be unable to prove tortious interference by BRMC in the instant case. The plaintiff has presented evidence that raises genuine issues of material fact about improper means (whether BRMC deducted revenues knowing such deductions were disallowed) and improper motives (whether BRMC sought to remove the plaintiff and take for itself the profitable Fertility Center and its outstanding receivables).18 See Melo-Tone Vend*191ing, Inc. v. Sherry, Inc., 39 Mass. App. Ct. 315, 316 (1995) (emphasizing that use of improper means or improper motive is necessary element of tortious interference with contract).

2. Motion to compel production of documents. Dr. Cardone appeals the denial of his motion to compel production of the Fertility Center’s patient records. The defendants objected to the plaintiff’s motion to compel on the ground that providing such information would violate the privacy and confidentiality interests of the patients. BRMC also rejected the plaintiff’s proposed “Confidentiality Agreement,” drafted to “assuage BRMC’s concern for patient confidentiality.” A Superior Court judge denied the plaintiff’s motion, with the exception of “aged accounts.” The defendants produced all documents responsive to the court’s order. The plaintiff’s renewed motion to compel was also denied.

“The conduct and scope of discovery is within the sound discretion of the judge.” Solimene v. B. Grauel & Co., KG, 399 Mass. 790, 799 (1987). See Bishop v. Klein, 380 Mass. 285, 288 (1980); Symmons v. O’Keeffe, 419 Mass. 288, 302 (1995); Buster v. George W. Moore, Inc., 438 Mass. at 653. Dr. Cardone must show that the denial of his motion to compel constituted such an abuse of discretion. A single justice of this court denied the plaintiff’s petition for relief, stating, “[t]he management of discovery is quintessentially the business of the trial judge.” See Beaupre v. Cliff Smith & Assocs., 50 Mass. App. Ct. 480, 485 (2000) (appellate courts accord great deference to discovery rulings of trial judges). Further, the single justice stated, “[t]he Superior Court judge’s limitations on discovery are consistent with concern for the patients’ rights of privacy.” See Alberts v. Devine, 395 Mass. 59, 68, cert, denied sub nom. Carroll v. Alberts, 474 U.S. 1013 (1985) (“all physicians owe their patients a duty, for violation of which the law provides a remedy, not to disclose without the patient’s consent medical information about *192the patient, except to meet a serious danger to the patient or others”).

Dr. Cardone sought production of documents relating to patients whom he may not have treated. Dr. Cardone was not entirely denied access to patient records. The Superior Court judge allowed limited discovery under circumstances that would not violate patient confidentiality. As we determine there was no abuse of discretion, we affirm the order of the trial court. See Beaupre v. Cliff Smith & Assocs., supra at 485.

3. Conclusion. The separate and final judgment as to Counts II and VI is reversed, and the matter is remanded to the Superior Court. The order denying the plaintiff’s motion to compel production of documents is affirmed.

So ordered.