Calculators5 min readUpdated: 2026-09-16
Principal Curtailment
Definition
Principal curtailment is an unscheduled extra payment made by a borrower applied directly to reduce the outstanding principal balance of a loan, bypassing accrued interest.
Detailed Technical Breakdown
In residential real estate financing, principal curtailment allows borrowers to accelerate amortization. Because monthly mortgage interest is calculated as a percentage of the remaining unpaid principal, curtailing the principal immediately lowers the balance upon which future interest is assessed, permanently compressing the loan term and generating compounding interest savings.
Key Technical Specifications
- Direct balance reduction: 100% of curtailment funds apply toward principal without interest deductions.
- Requires explicit borrower designation as 'Principal Only' to avoid servicer escrow misallocation.
- Compresses the amortization term without changing the contractual required monthly payment.
- Protected under the Dodd-Frank Act: residential mortgages generally cannot penalize principal curtailment.
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