What Is Buy-to-Let?
Buy-to-let (BTL) is buying a residential property to rent out for profit. As a BTL investor, you're a landlord: collecting rent, managing tenants, and maintaining the property.
Key Difference: BTL mortgages are different from residential mortgages. Lenders assess your affordability based on rental income, not your personal salary. The rent must cover the mortgage plus expenses.
BTL Deposit Requirements (2026)
Buy-to-let requires higher deposits than residential mortgages:
| Deposit % | LTV | Availability |
|---|---|---|
| 15% | 85% | Limited; specialist lenders only |
| 20% | 80% | Most major lenders offer this |
| 25% | 75% | Standard; widely available |
| 30%+ | 70% or less | Best rates; portfolio lenders available |
Note: Most lenders won't offer BTL mortgages below 75% LTV (25% deposit). Some have moved to 70% LTV minimum. This is stricter than residential mortgages (where 80% LTV is standard).
Rental Coverage Ratio (RCR)
The rental coverage ratio is the most important metric for BTL affordability. It measures whether rental income covers the mortgage and expenses.
Formula
Rental Coverage Ratio = Monthly Rental Income ÷ Monthly Mortgage Payment
Example
Property costs £200,000. Monthly rent: £1,200. Monthly mortgage: £800. RCR = £1,200 ÷ £800 = 1.5 (rent covers mortgage 1.5 times)
Lender Requirement: Most lenders require RCR of 1.25–1.45 (rent must cover mortgage 1.25–1.45 times). This buffer protects them if you have void periods or tenant issues.
How Lenders Test BTL Affordability
BTL affordability testing is different from residential. Lenders typically:
- Use "stressed" interest rates: Test your affordability at a higher rate than your deal rate (often base + 3%, regardless of your actual rate). This shows you can survive if rates rise.
- Apply rental coverage ratios: Rent must cover mortgage by at least 1.25–1.45 times
- Check your personal income: Some lenders still assess your own salary to ensure you can cover shortfalls
- Assess void risk: Deduct 20% from projected rental income (assumes 2–3 months vacant per year)
Real-World Calculation
Property rent: £1,200/month
Less void factor (20%): -£240
Effective rental income: £960/month
Mortgage at stressed rate (5.5%): £800/month
RCR = £960 ÷ £800 = 1.2 (many lenders require 1.25+, so this fails)
Total Costs of Buy-to-Let Ownership
Beyond the mortgage, BTL investors face ongoing costs:
- Maintenance & Repairs: Budget 1% of property value annually (emergencies can exceed this)
- Insurance: £20–50/month for buildings + contents insurance
- Council Tax/Ground Rent: Typically paid by tenant but verify lease
- Management Fees: If using an agent, 8–12% of rent collected
- Void Costs: Periods without tenants (mortgage still due, no rental income)
- Capital Gains Tax: When you sell, you owe CGT on gains (unlike primary residence)
- Income Tax: Rental income is taxable (net of expenses)
True BTL Budget Example
Gross monthly rent: £1,200
Mortgage: -£800
Maintenance (1% annually ÷ 12): -£167
Insurance: -£35
Void factor (20%): -£240
Net monthly profit: -£42 (NEGATIVE)
This property doesn't generate profit at current rent. You'd need £1,000+ monthly rent to break even.
BTL Strategy: Break-Even vs. Profit
Many UK BTL investors don't aim for immediate profit. Instead:
Break-Even Model
Rent covers mortgage + expenses. No monthly profit, but you gain equity (mortgage paydown) and benefit from property appreciation. Over 25 years, this can be lucrative.
Positive Cash Flow Model
Rent exceeds costs, generating monthly profit. Higher returns but requires either cheap property, high rent, or low mortgage (large deposit).
Reality Check: In most UK markets (2026), break-even is the norm. Positive cash flow requires good deals or significant deposits. Focus on capital appreciation + equity buildup, not monthly profit.
Personal Income Still Matters
Some lenders assess your personal income in addition to RCR:
- If rental income falls short of affordability tests, your salary can help bridge the gap
- Lenders may require you to cover shortfalls from your own income (especially if RCR is below 1.25)
- Your credit score and employment stability matter
Watch Out: If you have a low-income job and rely heavily on rental income, you may struggle with affordability. Many lenders don't count rental income from new properties until they've been rented for 6 months.
Is BTL Right for You?
Consider BTL if:
- You have 25%+ deposit saved
- You're comfortable with property management (or can pay for it)
- You can afford to carry the property if void (empty)
- You're in it for long-term capital appreciation, not quick profit
- Local rental market is strong (good rent-to-price ratio)
Avoid BTL if:
- You only have 10–15% deposit (deposit requirement too high)
- Local rental market is weak (low rents relative to property costs)
- You can't afford mortgage if property is vacant
- You're uncomfortable with tax complexity or tenant issues
- You need immediate monthly profit (most UK properties don't generate it)
BTL Checklist
- Confirm you have 20–25% deposit (most lenders won't go lower)
- Calculate realistic rental income (check local market rates)
- Apply 20% void factor to reduce rental income
- Calculate RCR (rental income ÷ mortgage payment) — aim for 1.3+
- Budget for maintenance, insurance, and management fees
- Verify the property has positive or break-even cash flow
- Check if your personal income helps meet affordability tests
- Speak with a mortgage broker experienced in BTL