Quick background, I'm a physician in a multi-physician practice owned by a major practice management company. I have a salaried position + production bonus that comes in as W2 income. My wife and I are having difficulty with getting pregnant and so are starting infertility treatments.

In order to pay for said treatments, I will be picking up some extra shifts at a different hospital (locum tenens) that will be 1099 income. Because it's going to a specific use, I need to maximize the cash flow in the immediate short term - so not looking to put any money in any tax sheltered accounts.

Having a hard time figuring out however what amount I should be keeping aside for taxes? Online tools I've seen don't seem to handle the W2 income very well. Just save something equal to what will be my marginal rate? More? Less? Set up a pass through (is this even an option if I also have W2 income?)?

I obviously don't want to run afoul of the IRS and pay the estimated taxes on time, but really want to have maximal availability of funds in case things get really expensive.


  • 1
    Note that since this is new 1099 income, you'd be covered by the "safe harbor" provision. As long as your total tax payments (withholding and any estimated tax payments) are IIRC at least 90% of your last year's tax, you're ok. You might want to check the IRS website to be sure of details.
    – jamesqf
    Nov 13, 2017 at 4:41

2 Answers 2


From my blog's discussion on 2017 tax rates.

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This is the final set of numbers. So, if you currently have, say $120K taxable income, every dollar above that starts getting taxed at 25%, until $153K, then 28%.

In other words, forecast your taxes based on the day job, but then the 1099 goes on top of that.

  • Plus the FICA taxes! A flat 15.3% unless he's over the cap. Nov 13, 2017 at 0:23


Joe's table helps. but think this way: there are two ways you can pay the taxes for your side-gig: either you can send a check quarterly to the Feds, OR, you can overwithhold at your real job to cover taxes at your sidegig. I'd do this in "arrears" -- after you get your first paycheck from sidegig, then adjust your real job's withholding.

Except (and Joe neglected this), you're still responsible for Social Security / Medicare Tax from your sidegig. I suspect your income at real-job is high enough that you stop paying Social Security Tax, so at least at this time of year you won't be subject to 15.4% Social Security Tax. However, that's NOT true for the 2.9% Medicare Tax. Remember that because you're an independent contractor being payed without withholding, YOU are responsible not only for the Medicare (and Social Security) taxes you'd be responsible for if a regular employee, but you're also responsible for what your employer's share as well.

  • Yes, I assumed Day job would take care of social security. Medicare no limit, true. Nov 13, 2017 at 0:35

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