CUMIPMT Function (OpenOffice Calc)

• Introduced: First release not established; documented by OpenOffice.org 3.3.
• Supported in: Apache OpenOffice 4.1.16; this is a verified release, not a final supported version.
• Scope: Desktop Calc, English function names and semicolon-separated formulas.
• Checked: October 14, 2026. Eight ordinary reference formulas were recalculated from generated ODF in 4.1.16 on Linux x86-64, Build 9816. Source and independent arithmetic were checked.

CUMIPMT sums the interest portions of scheduled loan payments over an inclusive period interval. For a positive borrowed principal, the result is normally negative because repayments leave the borrower. It is the core Calc function; the separate CUMIPMT_ADD compatibility identity is not established by these core-formula tests. Release implementation.

=CUMIPMT(Rate;Nper;PV;StartPeriod;EndPeriod;Type)

• Rate: interest rate per payment period, strictly positive for these cumulative functions.
• Nper: total number of payment periods; use a positive integer for an ordinary schedule.
• PV: positive loan principal.
• StartPeriod, EndPeriod: inclusive payment numbers from 1 through Nper. The implementation floors these two arguments.
• Type: 0 for end-of-period payments or 1 for beginning-of-period payments. All six arguments are required.

The native column contains saved 4.1.16 results; independent references use high-precision arithmetic and the stated source rules. Values are shown to twelve decimal places where needed.

For a 1000 loan, rate 1% per period and twelve end-of-period payments, the payment is approximately −88.848788678342. Total interest over periods 1 through 12 is approximately −66.185464140100. The first three payments contain −27.626651460782 of interest.

To present an interest cost as a positive report amount, negate the result deliberately. Keep the underlying cash-flow sign consistent when reconciling it with principal. If periods are months, a nominal annual 12% divided by 12 gives the stated 1% monthly rate; an effective annual 12% requires a different conversion.

For end-of-period timing, the first interest payment is −1000×0.01=−10. Subtracting interest from the signed payment gives principal repaid in that payment. Repeating the balance recurrence provides an independent check without calling CUMIPMT.

With beginning-of-period payments, the first interest portion is zero and the first payment immediately reduces the balance. The twelve-payment interest total falls to approximately −55.629172415941. CUMIPMT plus CUMPRINC over the same interval equals payment times the number of included payments; it is not a sum of unrelated yearly totals.

The release rejects nonpositive rates, principal or Nper, a start below 1, an end before the start and an end beyond Nper. Those guards were inspected; invalid inputs were not executed. Zero interest is outside this function’s accepted contract even though a zero-interest loan can be calculated directly.

Use Type 0 or 1. The core helper treats positive values as beginning timing rather than strictly checking this flag against two integers. Fractional start/end arguments are floored, so use explicit whole payment numbers to avoid silently changing the intended interval. Dates are not accepted as substitutes for period numbers.

IPMT, CUMPRINC, PMT.

• Function-specific release implementation
• ScGetRmz calculation
• ScGetZw calculation

The generated ODF produced the informational load warning “Not all attributes could be read.” The sheet was hard-recalculated and saved separately. All eight ordinary function identities, inputs and results were reconciled; a stale SUM cache changed from 999999 to 3 and an uncached SUM returned 7. This establishes the stated examples, not every workbook style or invalid input. Other explanatory identities are independent calculations. The authoring-tool XLSX was not executed in OpenOffice, and its preview values are not the native results reported here.