Splitting the payments does have one short time effect, the initial withholding may be lower.
Lets say the bonus is $20,000 and they make $60,000 a year. If the company treats it as a lump sum they may withhold 25% for federal taxes. This would mean that $5000 would be withheld right away. It would not matter if the friend was single, married, head of household or had many exemptions on their W-4. If the bonus was added to their monthly salary and appeared to the IRS as a regular monthly salary a bonus that large could cause even more withholding from IRS circular E:
Status Over but not over withhold of excess over—
Single $15,967 — $34,483.. $3,839.64 plus 33% —$15,967
Married $19,921 — $35,008.. $4,298.17 plus 33% —$19,921
That would put your friend into the the 33% withholding rate for that month. If they are paid every two weeks they could be in the 39.6% bracket for that pay check.
If they split it into multiple payments it could bring the withholding for those months back down to 25%. Of course that does spread out the payments, so if they need the cash to pay for the move that is a consideration.
with a generous signing bonus under the label of housing and
child-tuition support to help towards the burden of relocation.
If the friend meets the time and distance test they may be able to claim some moving expenses. This will allow them to reduce their income.
Your move will meet the distance test if your new main job location is
at least 50 miles farther from your former home than your old main job
location was from your former home. For example, if your old main job
location was 3 miles from your former home, your new main job location
must be at least 53 miles from that former home. You can use Worksheet
1 to see if you meet this test.
Time Test for Employees
If you are an employee, you must work full time for at least 39 weeks
during the first 12 months after you arrive in the general area of
your new job location (39-week test). Full-time employment depends on
what is usual for your type of work in your area.
For purposes of this test, the following four rules apply.
You count only your full-time work as an employee, not any work you do as a self-employed person.
You do not have to work for the same employer for all 39 weeks.
You do not have to work 39 weeks in a row.
You must work full time within the same general commuting area for all 39 weeks.
Once you pas those test you can claim expenses:
Deductible Moving Expenses
If you meet the requirements discussed earlier under Who Can Deduct
Moving Expenses, you can deduct the reasonable expenses of:
Moving your household goods and personal effects (including in-transit or foreign-move storage expenses), and
Traveling (including lodging but not meals) to your new home.
You cannot deduct any expenses for meals.
Of coure this savings won't happen until that taxes are filed next spring.