Background:
Have employer sponsored 401k/Roth 401k at work
Married filing jointly - exceed income to be able to contribute to Roth IRA

I still want to be able to contribute to a IRA, preferably one with posttax dollars so it can grow tax free so I looked into the Traditional to Roth IRA conversion.

At first, I thought I could contribute to a traditional IRA (I assumed all were funded w/ pretax money) so I contacted payroll to see if they could fund a traditional roth with pretax dollars.  They replied that they don't do pretax contributions.

I did some research and it appears if you exceed the income requirements and if you have an employer sponsored retirement account, you may not be eligible to contribue to a deductible (pretax funded) IRA.

It looks like I can fund it with post-tax dollars as a non-deductible contribution.

Fidelity confirmed that I can fund it as a non-deductible traditional IRA and then they can do the conversion to a Roth.  Since it's funded with post-tax dollars, there shouldn't be any penalty since i'm not withholding taxes.

They said i'd get a form 5498 but to consult a tax professional.  I asked if that was their typical canned statement they have to make and they said it is but to confirm just to be sure.

So I'm seeking the group wisdom here.

Do you see anything wrong with the plan to contribute to a non-deductible traditional Roth IRA with posttax dollars and then converting it to a Roth IRA?
Do you see any potential penalties or pitfalls?
What paperwork can I expect to have to file at tax time outside the 5498?
Is there any additional paperwork or caveats I should be aware of?

Thanks

A backdoor conversion is pretty common.  You have it all right so far.

Have had 1 conversion questioned by the IRS out of probably 100 or so.  Provided the documentation showing the conversion was from post tax dollars and it was not an issue.

You will be taxed on any growth at the time of conversion, if there is any.

No real paperwork at tax time.  Since your traditional contribution will not be deducted on your taxes there is a "non event" as taxes go.  
Keep all the paperwork with your tax stuff just in case you get a letter.

cool appreciate the info. the fidelity guy mentioned that he didn't think this loophole was intended so he wouldn't be surprised if it was closed later on.

what kind of paperwork should i keep?  
just a copy of my bank statement showing the withdrawal to fund the non-deductible traditional ira and a copy of the statement from fidelity showing the conversion?  
what do i need to do with the 5498, i assume i'll get prompted by turbotax to enter that correct?

As long as you don't have an existing Traditional IRA, everything will work as you plan.  If you have a Traditional IRA it will throw a major wrench in your plan.
Here is a link with a good bit of solid info on the subject: https://www.bogleheads.org/wiki/Backdoor_Roth_IRA

thanks for the link.  it'll be a brand new traditional IRA as i've only had a roth.  looks like i'm good to go.  wish i knew about this years ago, been foregoing IRA contributions for years now.

Roth conversions are pretty common. You are correct on everything, but Depending on how old you are and how far you are from retirement, you may want to delay the conversion. I usually suggest to people who are within five years of retirement that they should wait until they have stopped working and their ordinary income tax is reduced before performing roth conversion. Pay as little to uncle sam as possible, and then get a larger 401k balance converted into roth ira to grow capital gains tax free and avoid and required minimum distributions. If you are quite a way away from retirement, go for it. I have no business asking how much your pretax IRA accounts are worth, but if you are working with quite a few zeros, moving to a state without state income tax long enough to further reduce your tax liability is also an option many people take advantage of.

cool appreciate your insights.  in my late 30s so figure move it now and give it time to grow.  no state income tax here in texas so that doesn't come into play in this scenario.

Don't forget to do it for your spouse too.  Even if the spouse doesn't have a job, you can make a contribution for him/her as long as you are married filing jointly.

I used to have mine at Fidelity.  I'd make my traditional after tax contribution online in January.  It takes about a week for everything to clear and then the conversion is done online too.  Super easy.  Thing about Fidelity is that if you decide to move it somewhere else they'll charge you $50 to close the account.  Never had a problem.