When filling out my 2019 taxes this past weekend, I discovered a mistake I made in December.
In 2019 I had three taxable retirement fund money transactions:
1) April: RMD from inherited IRA to my brokerage account
2) June: trustee to trustee transfer of SEP IRA at Credit Union to Roth IRA at Schwab
3) December: trustee to trustee transfer from my employer's 401k to the same Roth IRA at Schwab
In December, when calculating the number of dollars to transfer from my 401k to my Roth, as I do every year, I estimated my 2019 income and determined the amount to transfer based on not exceeding the upper end of my tax bracket. When making this calculation I took into account the April RMD, but I forgot that I'd made the June SEP to Roth transfer (or perhaps I just assumed it was a SEP to Rollover IRA transfer and didn't look it up).
While figuring out my taxes last weekend, I discovered that the combination of all three transactions sent me into the next higher bracket. My mistake (not remembering the June SEP to Roth transfer when doing the December calculation) is going to cost me about $8000 more in taxes than I would have had to pay had I not made this mistake.
Is there any way to fix this situation, that is, is there any way I can recover the $8000 from the IRS? Note that I've filed an extension but paid the tax owed (including the $8000).