I'm not entirely sure what you mean by "doing the split". I know that California does a "blended" rate where the first 8 hrs of your shift are regular pay and the last 4 hrs are at an overtime rate. However, it sounds like you are speaking about some sort of split in wages which suggests participation in a tax advantage program.
If you are asking about a tax advantage program, I personally prefer to take a "set" wage and do the tax deductions myself. I find that for many locations, the standard amount that many companies take out does not fully take advantage of my entitled benefit.
For example, if I take the "meals and incidentials" that my company offers and take a pre-tax deduction of $420, then I must assume that I am working in a part of the country that only qualifies for the standard deduction. However, if I am working in Scottsdale, Arizona, where the price of meals and living can be a bit higher, then I am allowed a greater M&I deduction on my taxes. If I just take the dedction my company offered me that put more money in my pocket each week, I could possibly be throwing away hundreds of dollars versus taking my higher rate deduction come tax time.
Plus, if you are like most travelers, the tax advantage programs only muddy the water. Your recruiter says that you will be getting paid $32 an hour. Ok, then why does the contract I sign say that my base rate is $17.29?
When I have used tax advantage programs on my assignments, it actually does work out that my hourly is what the company said it would be. Like in the aforementioned example, my contract might say $17.29, but my final pay does reflect a rate of $32/hr. However, not all companies are the same in the way they structure the program or the amounts they deduct (because that would be too simple). There are nurses out there that make $32/hr, but their contract might read $8.32/hr. This type of rate should send red flags out to anyone.
Joseph Smith, a member of this site, prepares tax returns for travel professionals. He has a great page on his website that speaks to tax advantage programs and can be found here
http://www.traveltax.com/TravelRN/KnowledgeBase/TaxAdvantage.html
Joseph also evaluates tax advantage programs and he might still be doing that for free (with the hopes that you would use his services if you do use a tax professional for your returns). Even if he now charges a fee, it might be worthwhile to see if you particular company is operating where they need to be with regard to IRS regulations (especially if you earn considerably less on paper as opposed to your real take home wage).
All the sections on Joseph's website are a good read for the new traveler (he was the one I contacted to look over the section in my book on tax issues before I published). If you are going to participate in any tax advantage programs, then you need to read up on them further and truly understand their benefits and their downside. For example, a loan, or your retirement benefits, may be based on your reported income rates. What do you think a bank might say seeing that on paper you only appear to make $8.32 an hour? What could that rate do to you when social security bases its benefits on 35 years of your highest wages? These are all considerations when participating in tax advantage programs.
And finally, we haven't even touched on whether or not you truly qualify for a tax advantage program (do you really meet all the IRS qualifications of having a "tax home"?) All these things must be addressed when addressing any type of tax program provided by your travel company.
I know this might muddy the water a bit, but the more reading you do on the subject, the more understanding you will gain. Plus, if you just can't figure it out, call or message Joseph Smith and consider putting a tax professional in your corner.
I hope this is what you where speaking to and I hope this helps.
David Morrison
http://www.travelnursesbible.com