IPmt(n1, n2, n3, n4, n5)
n1, n2, or n3 are negative or 0.
Either n4 or n5 are negative.
If any parameter is null, the function returns null. If the payment amount (n3) is less than the monthly interest load, the function returns 0.
624.8839283142. The amount of interest repaid on a $30000 loan at 8.5% for the three months between the seventh month and the tenth month of the loan’s term.
7103.80833569485. The amount of interest repaid during the third year of the loan.
0, because the monthly payment is less than the interest the loan accrues during the month.

IPmt