It seems to discuss this here:
http://www.hmpadmin.com/docs/Supplem...tive_09-01.pdf
Looks like 25% window and gross difference and it won't cause a change.
The effective date of the trial period will be set forth in the Trial Period Plan. In most
cases, the effective date is the first day of the month following the servicer’s mailing of
the offer for the Trial Period Plan. The trial period extends for two (or more if necessary
to comply with applicable contractual obligations) additional payments after the effective
date.
Servicers are encouraged to require automated payment methods, such as automatic
payment drafting. If automatic payment drafting is required, it must be used by all HMP
borrowers, unless a borrower opts out.
If the verified income evidenced by the borrower’s documentation exceeds the initial
income information used by the servicer to place the borrower in the trial period by more
than 25 percent, the borrower must be reevaluated based on the program eligibility and
underwriting requirements. If this reevaluation determines that the borrower is still
eligible, new documents must be prepared and the borrower must restart the trial period.
If the verified income evidenced by the borrower’s documentation is less than the initial
income information used by the servicer to place the borrower in the trial period, or if the
verified income exceeds the initial income information by 25 percent or less, and the
borrower is still eligible, then the trial period will not restart and the trial period payments
will not change; provided, that verified income will be used to calculate the monthly
mortgage payment under the Agreement. (If, based on verified income the result of the
NPV test is “negative” for modification, the servicer is not obligated to perform the
modification.) However, if the servicer determines the borrower is not eligible for the
HMP based on verified income, the servicer must notify the borrower of that
determination and that any trial period payments made by the borrower will be applied to
the mortgage loan in accordance with the borrower’s current loan documents.