New/First Solo 401K: Contributions under Limit(s), but More than I intended/needed

Fingers crossed that I will relay my question in a coherent manner.  SHORT QUERY: I didn't contribute more than is allowed to my solo 401K for 2017, but I (somewhat accidentally) contributed way more than necessary and took our AGI too low. Can I correct that?

Long background story: I am 56 and had $84K of self-employment (sole proprietor) income in 2017 and established a solo 401K for myself ONLY on 12/28/17.  My husband has an S-Corp and I seldom know where his numbers will come in. In 2016 we paid a lot of tax because his income was surprisingly (to me) high in 2016. Thinking it would be the same in 2017, I contributed $3300 to my HSA, $13000 total in to IRAs for both of us, $24,000 EE to my new solo 401K and $15,500 ER to the solo 401K.  At the 11th hour of completing our 2017 taxes in September 2018, it became apparent that our AGI was going to be below 0 (!) after a big, unexpected (to me) loss came through from his business to our personal return.  For Affordable Care Act /Advanced Premium Tax Credits reasons we REALLY needed our AGI to be at least $13K higher than it was about to come out .

I had already wired the  2 separate (EE/ER) amounts in to my large brokerage plan provider, but I reduced line 28 on our tax return from $39,500 to $26,500. The brokerage's retirement accounts department had told me I could just send them a correction memo (which I did) and designate $13,000 of what I had sent in to be for 2018 rather than 2017.  Now that I read a lot of the great information on here, though, I can see that they shouldn't have told me this. I have evidence of the memo I sent them and when, but when I sign in to my account, they still have only the entries for $24,000 EE and $15,500 ER (i.e., they ignored the memo they breezily told me to send them).  

What recourse do I have? Our accountant just retired and the lovely person who has taken his place is hard for me to communicate with (couldn't reach him that last week due to holidays). Is there any way to legitimately recategorize/ recharacterize/ reclassify (not sure which is the right term) $13,000 of my solo 401K contributions from 2017?  If not, how about those darned IRA contributions I made? 

I thank you in advance for any feedback or insight as I hang my head in embarrassment. I realize my spouse and I need to improve our communication and that I am a poster child for the pitfalls of DIY solo 401K plans, big breezy brokerage house plans, etc. :/

To help us answer your question, please detail the dates and amounts contributed on those dates for the EE ($24,000) and ER ($15,500) that you are concerned with.

Also, normally one's 2017 tax return is completed long before today, so if you could describe the timing of when you filed your tax return for 2017 that might also be helpful.

Thank you for your reply. I was about to "save" a big edit/shortening of my LONG post when your reply came through (thank you again- I'm obviously losing sleep over this). I have now read back 30 or 40 pages in this forum and have come to realize I probably should have sent in a "Mistake of Fact" verification form to my brokerage house 401K department (instead of the informal memo they encouraged me to send in). (The "mistake of fact" being my understanding of what our income was/ the existence of the loss that was hitting us.)  Here are the dates:

12/28/17 Established solo 401K for my sole proprietorship - did not fund anything knowing that we always timely-file extensions

9/11/18 Knowing that I had made about $84K in 2017 and NOT knowing that my husband would be coming in with a loss, I wired $24K for a 2017 elective deferral and $15,500 for 2017 profit-sharing in to my brokerage house 401K department.

9/15/18 Husband's business filed - I learned of the loss that would be coming through

Late 9/18 Contacted brokerage house by phone. They told me not to sweat it and to write them to reclassify what I had sent in. I did so, asking for $13K of the profit-sharing to be for 2018 instead.

10/13/18 Filed personal return, with only $26,500 (instead of $39,500) on Line 28.  Did this confidently because brokerage house had been so reassuring on phone. 

12/29/18 Working on end-of-year tax matters and checked solo 401K online on brokerage's site. Saw that they hadn't followed through on "changing things" in my account as they said they would and started this panicked internet research after realizing how naive I'd been :/

*DISCLAIMER - this is hot air on the internet, not tax or legal advice - you need to consult your accountant on this.* I think your accountant will tell you that $13,000 of the $15,500 profit sharing contribution is deductible for 2018 instead of 2017 if you so choose (assuming you have income to support that deduction in 2018), it doesn't matter how the broker "classifies" it, and you don't have a problem.

On 12/30/2018 at 5:43 AM, lippy said:

*DISCLAIMER - this is hot air on the internet, not tax or legal advice - you need to consult your accountant on this.* I think your accountant will tell you that $13,000 of the $15,500 profit sharing contribution is deductible for 2018 instead of 2017 if you so choose (assuming you have income to support that deduction in 2018), it doesn't matter how the broker "classifies" it, and you don't have a problem.

Agreed.  Brokerage firms can code all they want but that info doesn't go anywhere but their own systems; it's not automatically reported to anyone (IRS).  If the IRS should ever review your records, under audit or otherwise, yes they will see the coding from the brokerage firm that they are 2017 contributions, but just keep your correspondence and your tax returns and show when you really deducted the contributions and that should take care of it.  This all means that you pretty much have to deduct the extra in 2018 though, it could be a 401(k) contribution or an employer profit sharing contribution.*

*Off topic but just for the record, you really can't scratch your head on Sep 11, 2018 and decide to take a $24,000 401(k) contribution for 2017.  That election should have been made by 12/31/17 (e.g. on a paper form).  "Everybody does it" and it's apparently not enforced at all.

If for some unlikely reason the above doesn't work for you, you also have the option of amending your 2017 return to treat your IRA contributions as nondeductible (you'll have to forever track those contributions on Form 8606 an nontaxable basis). Unfortunately it's too late to recharacterize those contributions as Roth contributions.

After considering your tax problem, certainly I understand why you would remove the IRA deduction from page 1 of your 2017 form 1040.  If the payment was made in 2018, then correcting the instruction to the IRA trustee works.

If the husband's S-corp provided W-2 income and pension contributions for 2017, then those payments could be 2018 payments with a corrected 1120-S for 2017 showing no pension costs.