Parachute Payment Withholding Requirements

[ERISA25]

If two parachute payments will be made in the same year, one in January and another in June, can an employer delay withholding the excess parachute tax (20%) until the June payment or must it withhold the 20% for both payments. IRC section 4999 indicates that parachute taxes are subject to withholding just like ordinary income under IRC section 3402. I was wondering if there was any type of exception that would allow a company to avoid withholding the parachute tax on the first payment and withhold instead the entire 20% when the june payment comes due. i.e. if payment of $1,000 were made on January 31, and a second payment of $1,000 were made on June 31, and there is a $400 parachute tax, can you withhold the entire $400 from the second payment, rather than deducting $200 from the January payment and $200 from the June payment? Thanks.