I have 2 nearly identical spreadsheets each with a sheet that calculates income taxes on wages. Part of the calculation is circular, so I have chosen the ENABLE ITERATIVE CALCULATIONS with 100 Iterations in the File Options area. In the 2018 version of this calculation, it works, no errors. I updated the 2018 spreadsheet to include 2019 tax rates, very few other changes. But in the 2019 version, the circular formulas all indicate #REF errors. The formulas are identical in the two files.