I believe that ProSeries 2024 has Form 1120S, pages 3-5, Schedule K, Line 12c (Investment Interest Expense) erroneously linking to Form 1120S, Line 26 (Other Deductions) for purposes of computing taxable income. It is my understanding that Investment Interest Expense is NOT deductible by the S corporation in determining taxable income for the built-in gains (BIG) tax under IRC § 1374. Under Treas. Reg. § 1.1374-2(a), only business interest expense that is properly allocable to a trade or business is deductible at the S corporation level and reduces net recognized built-in gain (NRBIG) for BIG tax purposes. Investment interest expense must be separately stated and passed through to shareholders (including ESBTs), who may deduct it on their own returns subject to the § 163(d) limitation. It is not included in the ordering or limitation rules for NRBIG and should not reduce the S corporation’s taxable income for BIG tax purposes [1] [2] [3].  For now, I'm overriding the deduction. Hoping someone has a better workaround. 

[1] statute Sec. 1374 Tax imposed on certain built-in gains
[2] regulation Sec. 1.1374-2 Net recognized built-in gain.
[3] admin Rev. Rul. 84-131