Interest-only BTL mechanics and PRA ICR stress test
The PRA's ICR stress test is the primary constraint on interest-only BTL borrowing capacity — it must be met at the stressed rate (5.5-7.5%), not the product rate.
- Interest-only mechanics: monthly payment = loan × annual rate ÷ 12; entire capital balance outstanding at term end; lower monthly payments than capital repayment but requires a separate repayment vehicle or sale strategy
- ICR stress test: lenders must test affordability at a stressed rate (higher of 5.5% or product rate + 2%; typically 5.5-7.5%); ICR minimum 125% for basic-rate (20%) taxpayers; 145% for higher-rate (40%+) taxpayers; maximum loan = gross monthly rent ÷ ICR × 12 ÷ stressed rate; example: £1,000 rent; 145% ICR; 7% stressed rate: max loan ≈ £118,000
- Rising rates reduced BTL borrowing capacity: when stressed rates were 5.5% (low base rate era), an £800 pcm rent supported a larger loan than when stressed rates rose to 7.5%; landlords with highly leveraged portfolios fixed when rates were low may find they cannot refinance at the same LTV when their fixed rate expires
- PRA 2017 portfolio landlord rules: 4+ mortgaged BTL properties triggers portfolio landlord status; lender must assess aggregate portfolio LTV; aggregate portfolio ICR across all mortgaged BTL properties at stressed rates; and may require a portfolio business plan (spreadsheet of all properties — address; value; mortgage balance; rate; maturity; rent; payment; plus narrative); a weak property in the portfolio can affect the refinancing of stronger properties
Section 24 — the tax cost of leverage on interest-only BTL portfolios
Section 24 of the Finance Act 2015 replaced mortgage interest deduction with a 20% basic-rate tax credit from April 2020 — devastating for highly leveraged 40% taxpayers.
- Section 24 mechanism: from April 2020, individual landlords cannot deduct mortgage interest from rental income for income tax purposes; instead they receive a 20% basic-rate tax credit on finance costs; Section 24 does NOT apply to limited companies (which can still deduct mortgage interest in full)
- Section 24 worked example (40% taxpayer): £1,500 pcm gross rent; £900 pcm interest (£10,800 pa); other expenses £200 pcm (£2,400 pa); pre-S24: tax on (£18,000-£10,800-£2,400)=£4,800 at 40%=£1,920 net tax; post-S24: tax on (£18,000-£2,400)=£15,600 at 40%=£6,240 less 20% credit on £10,800=£2,160 = net tax £4,080; net after-tax return fell from £2,880 to £720 — a 75% reduction in net income
- Repayment vehicles: sale of property at term end (most common; reliance on capital growth); ISA/investment portfolio; pension 25% tax-free lump sum; rental income savings; partial switch to capital repayment in final years; plan repayment vehicle from the outset — do not leave to the final 1-2 years before maturity
- End-of-term risk: inability to refinance due to age (most lenders maximum age at maturity 75-85); ICR shortfall if stressed rates at maturity are higher than when property was originally mortgaged; options if ICR insufficient: increase rent; partial capital repayment to reduce loan; sell property; switch to capital repayment