I am seeing what I believe is an error in calculations on form 8606 for non-deductible IRAs. It is showing an incorrect basis on line 14. How do I correct it?

[be1]

This appears to be a bug in the software, and the customer service line has no idea how to report it or fix the problem.  What do I do from here?

Line 1 = $5500 (correct)
Line 2 = $5375 (correct)
Line 3 = $10875 (correct)
Line 4 = blank (correct)
Line 5 = $10875 (correct)

Line 6-12 it didn't fill in, but my calculations they should be:
Line 6 = $0
Line 7 = $0
Line 8 = $10428
Line 9 = $10428
Line 10 = 1.04286536
Line 11 = $10875
Line 12 = $0

Then given those
Line 13 should be $10875, but TT has it as $10428
Line 14 should be $0, but TT has it as $447

Line 16 = $10428 (correct)
Line 17 should be $10875 but TT has it as $10428
Line 18 should be -$447 but TT has it as $0

[dmertz · Accepted solution]

TurboTax's calculation is correct.  The nontaxable amount cannot exceed the amount of your Roth conversion.  No amounts on Form 8606 are permitted to be negative.

The blank lines 6 through 12 indicate that TurboTax is using the Taxable IRA Distribution Worksheet to calculate the taxable amount of your Roth conversion.  Even if TurboTax did the calculation directly on Form 8606, the result would still be the same, $10,428.  The remaining $447 of basis carries forward now that there is no deduction for unrecoverable basis for tax years 2018 through 2025.

Line 10 of your own calculation is wrong.  The amount on line 10 is capped at 1.000.  This error of yours is leading to incorrect amounts for your calculations of lines 11, 13, 14, 17 and 18.