nnk13, if your taxpayer is over the income limits and subject to the Wages Limit/ UBIA limits, and some QBI activities are being limited, then in certain cases, aggregating activities can result in a larger total QBI deduction.  If taxpayer is below the income limit, there probably is not a good reason to aggregate. 

In general, a taxpayer can aggregate businesses only if the five aggregation requirements listed below are satisfied:

1. The same person or group of persons directly or indirectly owns 50% or more of each business to be aggregated. For businesses operated by an S corporation, that means owning 50% or more of the issued and outstanding shares. For businesses operated by partnerships (including LLCs treated as partnerships for tax purposes), that means owning 50% or more of the capital or profits interests. For purposes of applying the 50% ownership rule, a taxpayer is also considered to own the interest in each business that’s owned directly or indirectly by his or her spouse, children, grandchildren or parents.
2. The preceding 50% ownership picture exists for a majority of the tax year in which the items for each business to be aggregated are included in the taxpayer’s income.
3. All the tax items attributable to each business to be aggregated are reported on returns with the same tax year end.
4. None of the businesses to be aggregated is a specified service business. Income from a specified service business generally doesn’t count as QBI. The service business disallowance rule is phased in over the same taxable income ranges that apply to the limitations based on W-2 wages and the UBIA of qualified property.
5. The businesses to be aggregated must satisfy at least two of the following three requirements:
   • The businesses provide products and services that are the same or customarily offered together (for example, a gas station and a car wash).
   • The businesses share facilities or significant centralized business elements (such as personnel, accounting, legal, manufacturing, purchasing, human resources or information technology).
   • The businesses are operated in coordination with or in reliance on each other. (For example, they have supply chain interdependencies.)

Good luck!