If the distribution is eligible for rollover (it is not an RMD, distribution of an excess contribution, a deemed distribution due to 401(k) loan default or a hardship distribution), the 401(k) plan is required to withhold a minimum of 20%, but as fanfare said, 20% will almost certainly not be sufficient to cover your additional income tax and early-distribution penalty resulting from a $90k 401(k) distribution. If you wait until April 2019 and have a balance due, you could end up with a tax underpayment penalty on top of everything else.
