First, you must meet a triggering event in order to take a distribution from a 401k including a ROBS 401k. Distribution triggering events include retirement age (usually age 59 1/2) and no longer working for the employer that sponsors the 401k. Regarding taking a distribution from a 401k plan and then paying back within 60 days, the mandatory federal upfront tax of 20% withholding requirement would still apply. For example, if you distribute $10,000 you will receive $8,000 since a 20% federal tax withholding would apply. You woud still be able to deposit $10,000 within 60 days.
Also, distribution reporting will apply. See the following form the IRS page: https://www.irs.gov/individuals/international-taxpayers/pensions-and-annuity-withholding
Depositing and Reporting Withheld Taxes
Payers report income tax withholding from pensions, annuities, 403(b) plans, governmental section 457(b) plans, and IRAs on Form 945, Annual Return of Withheld Federal Income Tax. Do not report these withheld amounts on Form 941, Employers Quarterly Federal Tax Return. You must furnish Form 1099-R, Distributions From Pensions, Annuities, Retirement or Profit-Sharing Plans, IRAs, Insurance Contracts, etc. to payees and the IRS.
Deposit such income tax withholding with any other nonpayroll withholding reported on Form 945 (e.g., backup withholding). Do not combine the Form 945 deposits with deposits for payroll taxes reported on Form 941 or NRA Withholding taxes reported on Form 1042. Circular E and the separate Instructions for Form 945 include information on the deposit rules for Form 945.
For information on withholding and reporting on pensions and annuities paid to foreign persons, refer to Pensions, Annuities, and Alimony (Income Code 15) in Publication 515, Withholding of Tax on Nonresident Aliens and Foreign Entities.
