The 1411 regs, as far as I know, have not changed, so let's look at them.
1.1411-1(f)
(3) Properly allocable deductions described in section 63(d). In determining net investment income, the following itemized deductions are taken into account:
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(ii) Investment expenses . Investment expenses (as defined in section 163(d)(4)(C)).
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(7) Application of limitations under sections 67 and 68 . Any deductions described in this paragraph (f) that are subject to section 67 (the 2-percent floor on miscellaneous itemized deductions) or section 68 (the overall limitation on itemized deductions) are allowed in determining net investment income only to the extent the items are deductible for chapter 1 purposes after the application of sections 67 and 68. For this purpose, section 67 applies before section 68. The amount of deductions subject to sections 67 and 68 that may be deducted in determining net investment income after the application of sections 67 and 68 is determined as described in paragraph (f)(7)(i) and (f)(7)(ii) of this section.
(It goes on from there in detail).
The preamble to those regs. contains some comments to consider.
D. Properly allocable deductions described in section 1411(c)(1)(b)
Section 1411(c)(1)(B) provides that net investment income includes deductions allowed by subtitle A that are properly allocable to gross income or net gain described in section 1411(c)(1)(A). Section 1.1411–4(f)(1)(i) of the proposed regulations provided that “[u]nless specifically stated otherwise, only properly allocable deductions described in this paragraph (f) may be taken into account in determining net investment income.” Specifically, proposed §1.1411–4(f)(3) provided that properly allocable deductions include: (A) investment interest expense, (B) investment expenses described in section 163(d)(4)(C), and (C) state, local, and foreign income taxes described in section 164(a)(3). The Treasury Department and the IRS intend this rule to limit the deductions against net investment income to those specifically enumerated in paragraph (f).
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... the Treasury Department and the IRS acknowledge that flexibility is needed within §1.1411–4(f) so that future changes in law or circumstances can be more easily integrated into the regulations. Although the cross-references in §1.1411–4(f)(2) to deductions described in section 62(a) provide section 1411(c)(1)(B) flexibility to automatically take into account additions or changes to chapter 1 deductions attributable to trades or business, rents, and royalties, these regulations would have to be amended to expand properly allocable deductions in the event of such changes not captured by section 62(a)(1) or 62(a)(4). To strike a balance between the intent of the proposed rule (to provide a specific list of deductions to limit uncertainty and controversy) and the recognized value of future flexibility inherent in the commentators’ recommendation, §1.1411–4(f)(6) of the final regulations allows the Treasury Department and the IRS to publish additional guidance in the Internal Revenue Bulletin that expands the list of properly allocable deductions.