CalMachine is an interest calculation engine that is not tied to the loan ledger. From any system, not just the core lending system, at any point in time — past, present or future, it calculates normal, overdue and refund interest in a single call.
Not just the base date — any point in time
Outside the core — called from any system
Not three APIs — one single call
Core-embedded calculation works from the base date stored in the ledger DB, only inside the core, with a separate API for each interest type. CalMachine is parameter-driven: pass the required values and it calculates every interest type at once — from any system, at any point in time.
| Item | AS-IS · Core-embedded calculation | CalMachine · Independent engine |
|---|---|---|
| Architecture | ||
| Where it runs | Only inside the ledger (core). Other systems must call the core | Anywhere outside the core — API · Java library · batch jar |
| Required input | Needs the ledger DB and transaction history | Only loan terms · rate history · holidays |
| Core load | Every mobile/internet banking inquiry and simulation hits core transactions | Inquiries and simulations run outside the core — zero core DB load |
| Cross-system results | Channel, credit and closing systems each keep their own logic → inconsistent results | One engine — same input, same result in every system |
| Change · Operations | ||
| Rule changes | Modify core programs → test → wait for release window | Rates, day count, cycles, holidays, rounding via parameter changes |
| New product checks | Hard to see results before the core is changed | Enter product terms for an instant pre-launch simulation |
| Past-date recalculation | Disputes and audits require restoring ledger history — takes days | Instant recalculation at any past, present or future date |
| Calculation evidence | Mostly result amounts — tracing the basis needs separate analysis | Per installment: days · applied rate · balance · rounding |
| Verification · Migration | ||
| Result verification | Self-check — core results checked by the core | Independent reconciliation against core results |
| Regression tests | Rebuilt for every project, hard to maintain after go-live | 13,000+ regression cases and the combinatorial set are delivered · reproducible with one command |
| Next-gen · replacement | Rebuild interest logic and compare old/new results by hand | Reuse the engine · parallel old/new reconciliation for a seamless switch |
※ Based on a typical core-embedded structure; actual implementations vary by institution. CalMachine does not replace core results — it handles calculation and verification outside the core.
An actual result calculated in one call with no loan ledger — normal interest on the current balance, installment and interest overdue interest, including acceleration (loss of the benefit of term).
Principal KRW 100M · equal principal · 5.50% p.a. · overdue rate 10.50% · overdue from 10/21 · acceleration 10/27
Enter just one acceleration date, 2025-10-27. From that day the full KRW 100M principal becomes overdue, principal overdue interest (row 6) is calculated automatically, and normal, installment and interest overdue amounts stop at 10/26.
The same account calculated without acceleration. Normal interest and installment/interest overdue amounts continue to the query date.
← Swipe the table sideways to see all columns
| No. | Type | Base amount | Start | End | Days | Rate(%) | Amount |
|---|---|---|---|---|---|---|---|
| 1 | Principal due | 8,333,333 | 2025/09/21 | 2025/10/20 | 30 | — | 8,333,333 |
| 2 | Normal interest | 100,000,000 | 2025/09/21 | 2025/10/20 | 30 | 5.50 | 452,054 |
| 3 | Installment overdue | 8,333,333 | 2025/10/21 | 2025/10/26 | 6 | 10.50 | 14,383 |
| 4 | Interest overdue | 452,054 | 2025/10/21 | 2025/10/26 | 6 | 10.50 | 780 |
| 5 | Normal interest | 91,666,667 | 2025/10/21 | 2025/10/26 | 6 | 5.50 | 82,876 |
| 6 | Principal overdue Acceleration | 100,000,000 | 2025/10/27 | 2025/10/28 | 2 | 10.50 | 57,534 |
| No. | Type | Base amount | Start | End | Days | Rate(%) | Amount |
|---|---|---|---|---|---|---|---|
| 1 | Principal due | 8,333,333 | 2025/09/21 | 2025/10/20 | 30 | — | 8,333,333 |
| 2 | Normal interest | 100,000,000 | 2025/09/21 | 2025/10/20 | 30 | 5.50 | 452,054 |
| 3 | Installment overdue | 8,333,333 | 2025/10/21 | 2025/10/28 | 8 | 10.50 | 19,178 |
| 4 | Interest overdue | 452,054 | 2025/10/21 | 2025/10/28 | 8 | 10.50 | 1,040 |
| 5 | Normal interest | 91,666,667 | 2025/10/21 | 2025/10/28 | 8 | 5.50 | 110,502 |
※ Actual CalMachine engine output (calculation date 2025-10-29). Refund interest, accrued interest and prepayment fees are returned in the same response.
We demo on a single laptop with no external network, so it works even in air-gapped environments. It is best viewed together with your project, lending and audit teams. Online demos are also available for overseas institutions.
Tell us your organization, department and one product condition you want to see.
We contact you within 2 business days to set a date.
We calculate your product condition on the spot and answer questions live.
If you wish, we continue with a comparison against your current system using sample accounts.
Interest in advance or in arrears per repayment method, separate principal and interest cycles — every variable that affects interest is a parameter.
| Interest in advance | Bullet · equal payment · equal principal · custom principal |
| Interest in arrears | Bullet · equal payment · equal principal · custom principal · step-up · balloon (with grace period) |
| Day count | ACT/365 · ACT/360 · 30/360 · 365/366 mixed · one-side / both-side inclusion |
| Rates | Fixed · floating (COFIX · KOFR · SOFR · CD, etc.) · rate-period splitting · spreads |
| Cycles · holidays | Separate principal/interest cycles · advance/arrears · holiday rules · interest end-date options · multi-country holidays (KR · US · JP) |
| Delinquency · repayment | Principal / interest / installment overdue · acceleration · prepayment · refund interest · interest on current balance |
| Corporate · PF | Interest in advance · interest end date moved to the preceding business day on holidays, and other corporate lending rules |
Out of scope: overdraft lines (daily-balance accumulation in the deposit system)
Three tiers, each guarding against a different risk: does it match the answer key, does it follow the rules under any combination of conditions, and does it match your system.
Checks interest formula · day count · reversed periods · overdue start date · refund interest · next due date · periods before loan start · overlapping periods · principal and total collection reconciliation. A case passes only when two independent engines give the same answer for the same input.
Give us basic account information and we verify right away, at any point in time. No upfront scheduling or system integration — we compare results for any date (past, present, future) using only data you already have.
With one of your product conditions, watch normal, overdue and refund interest calculated in one call — at any point: past, today or future.
Prefer to explore on your own first? → Try the 1-minute calculator