Finance Interest Roll-Up

Finance interest rolls up on a drawdown profile (S-curve for new build). Average outstanding balance over duration runs roughly 50 percent of peak debt. The workbench applies that approximation. Add arrangement (1 to 2 percent), monitoring (monthly), and exit (1 to 2 percent) fees on top.

S-curve assumption

New-build drawdown follows an S-curve: slow start, rapid mid-build draws, slow tail. Average outstanding balance is roughly 50 percent of peak debt over the build period. The workbench interest line uses this 50 percent approximation.

All-in fees

  • Arrangement: 1 to 2 percent of facility on day-one drawdown.
  • Monitoring surveyor: £1,500 to £3,500 per monthly visit.
  • Exit / non-utilisation: 1 to 2 percent of facility at redemption.
  • Broker fee (if used): 0.5 to 1 percent of facility, deducted at drawdown.

IRR vs flat rate

A 9.5 percent flat-rate quote on a 12-month facility is not the same as a 9.5 percent IRR. With arrangement and exit fees compressed into a short hold, IRR can run 12 to 15 percent. Always model the all-in IRR for lender selection.

UK Finance data and research· Q1 2026Appraisal model reviewed by Oliver Wakefield-Smith (data integrity) with chartered-surveyor (MRICS) and CTA tax review. No affiliate links.