Returns the total capital repaid on a loan in specified periodic payments.
CUMPRINC(rate, numperiods, presentvalue, start, end, type)
rate: the interest rate per period.
numperiods: the total number of payment periods in the term.
presentvalue: the initial sum borrowed.
start: the first period to include. Periods are numbered beginning with 1.
end: the last period to include.
type: when payments are made:
0 - at the end of each period.
1 - at the start of each period (including a payment at the start of the term).
With a fixed rate loan, where you make a constant payment each period to pay off the loan over the term, some of each period payment is interest on the outstanding capital, and some is a repayment of capital. Over time (as you pay off capital), the interest becomes less and the capital repayment becomes more.
IPMT returns the interest in the payment of a specified period. PPMT returns the capital repaid in the payment of that period. Together they add up to the actual payment, given by PMT.
CUMPRINC returns the total capital repaid in payments during the periods start to end inclusive - that is, the sum of PPMT over that time.
CUMPRINC(5.5%/12, 12*2, 5000, 4, 6, 0)
returns -603.63 in currency units. You took out a 2 year loan of 5000 currency units at a yearly interest rate of 5.5%, making monthly payments at the end of the month. The capital you repaid in the 4th-6th months inclusive is 603.63 currency units. It is given as negative because you pay it.