How is this situation looked at when re-certifying an ICR repayment plan?
Base pay plus commission. The base pay is guaranteed but commission is not and some months there is no commission that was paid.
Would you manually send the re-certification in and get a letter from your employer stating your guaranteed amount?
You would use your tax return with your AGI. That's always the best approach each year.
If you use the "alternative method" to certify your income, they use your gross pay, not net pay, so you usually end up with a higher monthly payment. The only time the alternative method makes sense is if you lost your job and have no income.