at most 3 number for the 199A deduction (20Z)
1) business income or (loss)
2) w-2 wages ( this can be zero if no wages were paid (the code and regs give you various ways to determine this number
2) unadjusted basis immediately after acquisition (UBIA) also can be zero
the rules for this are complex
from code sec 199A
(6)Qualified property (UBIA)
For purposes of this section:
(A)In general
The term “qualified property” means, with respect to any qualified trade or business for a taxable year, tangible property of a character subject to the allowance for depreciation under section 167—
(i)which is held by, and available for use in, the qualified trade or business at the close of the taxable year,
(ii)which is used at any point during the taxable year in the production of qualified business income, and
(iii)the depreciable period for which has not ended before the close of the taxable year.
(B)Depreciable period
The term “depreciable period” means, with respect to qualified property of a taxpayer, the period beginning on the date the property was first placed in service by the taxpayer and ending on the later of—
(i)the date that is 10 years after such date, or
(ii)the last day of the last full year in the applicable recovery period that would apply to the property under section 168 (determined without regard to subsection (g) thereof).
even more complex are the REGs that address UBIA for partnerships
(ii) UBIA of qualified property held by a partnership. In the case of qualified property held by a partnership, each partner's share of the UBIA of qualified property is determined in accordance with how the partnership would allocate depreciation under § 1.704-1(b)(2)(iv)(g) on the last day of the taxable year.
(iv) UBIA and section 743(b) basis adjustments -
(A) In general. A partner will be allowed to take into account UBIA with respect to an item of qualified property in addition to the amount of UBIA with respect to such qualified property determined under paragraphs (a)(3)(i) and (c) of this section and allocated to such partner under paragraph (a)(3)(ii) of this section to the extent of the partner's excess section 743(b) basis adjustment with respect to such item of qualified property.
(B) Excess section 743(b) basis adjustments. A partner's excess section 743(b) basis adjustment is an amount that is determined with respect to each item of qualified property and is equal to an amount that would represent the partner's section 743(b) basis adjustment with respect to the same item of qualified property, as determined under §§ 1.743-1(b) and 1.755-1, but calculated as if the adjusted basis of all of the partnership's property was equal to the UBIA of such property. The absolute value of the excess section 743(b) basis adjustment cannot exceed the absolute value of the total section 743(b) basis adjustment with respect to qualified property.
(C) Computation of partner's share of UBIA with excess section 743(b) basis adjustments. The partnership first computes its UBIA with respect to qualified property under paragraphs (a)(3)(i) and (c) of this section and allocates such UBIA under paragraph (a)(3)(ii) of this section. If the sum of the excess section 743(b) basis adjustment for all of the items of qualified property is a negative number, that amount will be subtracted from the partner's UBIA of qualified property determined under paragraphs (a)(3)(i) and (c) of this section and allocated under paragraph (a)(3)(ii) of this section. A partner's UBIA of qualified property may not be below $0. Excess section 743(b) basis adjustments are computed with respect to all section 743(b) adjustments, including adjustments made as a result of a substantial built-in loss under section 743(d).
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IRC 743 deals with property contributed by a partner with built-in loss or basis adjustment attributable to IRC 754 (step up in basis)
