I plan to withdraw money from my 401B account. 1) How much tax should I pay upfront? 2) Can I spread that amount over 3 years or do i have to report all this year?

[xmasbaby0]

If you take money out of a retirement account in 2020, you will receive a 1099R in late January, which you will have to enter on your 2020 tax return.  No, you cannot spread the tax out.  The custodian of the account will withhold some federal tax which will be shown on your 1099R.  But the tax you owe will be determined by the total amount of your 2020 income--which we do not know---so we cannot tell you how much tax you will owe for the distribution.  You will be taxed at the rate for your tax bracket.

[Opus 17]

Do you mean 403(b)?  Or 401(a)?

If you can certify that the withdrawal was due to a COVID-19-related hardship, there are several special provisions that apply (for withdrawals up to $100,000 per person).

1. you are exempt from the extra 10% penalty for early withdrawal if you are under age 59-1/2
2. you can spread the tax out over 3 years
3. you can return the money to the account within 3 years so it can continue to grow for your retirement.

We can't tell you how much tax to have withheld, it depends on your other income, deductions and credits.  The income tax rates for most taxpayers are 15%, 22% or 24%.  If you wanted to spread the tax out over 3 years, you could have less withheld this year, but you would have to come up with the rest next year unless you return part of the distribution to the account instead. 

See here

https://www.irs.gov/newsroom/irs-provides-guidance-under-the-cares-act-to-taxpayers-with-net-operati...

You can also use the IRS calculator to estimate the tax you will owe. 

https://www.irs.gov/individuals/tax-withholding-estimator

If the withdrawal is NOT related to a COVID-19 hardship, then you will be subject to regular income tax, plus a 10% penalty for early withdrawal if you are under age 59-1/2.  (There may be an exception to the penalty for certain types of retirement accounts if you retire due to permanent disability.)  Taxes would be 15%, 22% or 24% for most taxpayers.  However, if you are retired and collecting social security, this additional income could also cause more of your social security to be taxed.  You can't spread out the taxes on a regular retirement withdrawal.