I’m concerned about double counting. The respondent instructions for INCBUS00 say ‘exclude profit from incorporated [farm] business’ but the description of the ACS variable INCBUS00 says ‘no distiction is made between incorportated and unincorporated.’
This is a bit confusing. I’ll send a note to the IPUMS USA Team to clarify this detail in the documentation.
To answer the question: Values of INCBUS00 excludes income from incorporated businesses. This is noted in two places. First, as you point out, the questionnaire textnotes otherwise. Second, the comparability tab suggests that to compare data between INCBUS00 and INCBUS, amounts from INCFARM should be added to INCBUS. However, INCBUS also explicitly excludes income from incorporated enterprises, as noted on the INCBUS description tab.