Private equity firm Thompson Street Capital Partners is buying Software Technology Inc. (STI), a provider of financial and practice management software for the legal industry, in partnership with the target’s management. Financial terms of the deal were not disclosed.

STI develops and manufactures Tabs3, the company’s flagship software program, to assist small and mid-sized law firms with billing, time-keeping, automating back-office workflows, and other financial management functions. The target, based in Lincoln, Nebraska, was founded in 1979 and services more than 50,000 attorneys at approximately 10,000 law firms. STI’s other software technology, called PracticeMaster, is the developer’s non-financial practice management product. PracticeMaster helps attorneys manage cases, contacts, calendars and legal documents. Both Tabs3 and PracticeMaster can work as a standalone product or can be fully integrated using one interface.

Thompson Street, founded in 2000, is a St. Louis, Missouri-based private firm investing in founder-led companies. The PE firm targets middle-market businesses that have up to $15 million in Ebitda across several sectors, including: business services, health care, and engineering. Thompson Street raised a middle market private equity fund, called TSCP IV, in Dec. 2015 with nearly $640 million in capital commitments. The firm’s current portfolio includes: Logan’s Linens, which rents linens to health care facilities; Clinical Research Data Group, a full service research organization providing clinical data management, medical writing, and biostatistics services to the pharmaceutical and biotech industry; and building products manufacturer Stone Panel.

Middle-market deals involving software technology for law firms include: Omers Private Equity and Harvest Partners LP’s joint-deal to buy legal tech provider Epiq Systems Inc. (Nasdaq: Epic) for $1 billion; Roper Technologies Inc.’s (NYSE: ROP) investment in Aderant Holdings Inc., a software maker that helps law firms manage caseloads, billing and docket calendars, from Madison Dearborn Partners; Hyland Software’s completed acquisition of case management software company LawLogix Group, backed by Thoma Bravo, from PNC Riverarch Capital and Akoya Capital Partners. Cascadia Capital served as financial adviser to STI.