INCTOT in IPUMS-CPS is supposed to be “the sum of several different types of income that the survey asked respondents to report.” (https://cps.ipums.org/cps-action/vari…)
However in a(n admittedly small) share of the observations that is not true. For example, for survey year 2018 (ASEC), these are the differences between the supposed sum of the components and INCTOT (note that, despite the documentation linked to above, the component INCALIM is not available after 2014):
Do you have any insight into the source of these “errors”, especially for the larger amounts. I note that 99999 is often a CPS code used for missing data.