While we were importing vendor master during our implementation, the 1099 box did not get updated.
Later I researched it a bit to find out where the issue was. In the Vendor DMF mapping, there are 2 fields in the staging table that are pointing to the target mapping. Which means in the DMF you’d need to fill in both fields “Tax1099Box” and “Tax1099Type” to get the data updated to the target.
Essentially your DMF template should have the below columns filled in with the data as shown below.
You can find the Tax 1099 Type in the Tax 1099 fields against each 1009 box. So whenever you update the vendor template with the 1099 box, make sure you also update Tax1099Type along with it.