On any UK BTL forum, half the threads are about yield and half are about cashflow. The two sides talk past each other because they're measuring different things and optimising for different outcomes.
Yield asks: “Is this property a productive asset?”
Cashflow asks: “Will this property feed me each month?”
Both answers matter. The mistake is using one as if it told you the other.
Net yield: the asset-quality metric
Net yield = Net annual income ÷ Total acquisition cost
Net annual income is gross rent minus operating costs — typically void allowance, management fee, maintenance, insurance, ground rent, service charge. Total acquisition cost is purchase price plus SDLT, legal fees, survey, refurb (if any), and any other one-off costs to get the property tenant-ready.
Worked example. £200,000 property, £14,400 annual rent, 28% operating costs (so net income = £10,368). SDLT (BTL surcharge) £11,500. Legal £1,500. Survey £450. No refurb. Total acquisition cost = £213,450. Net yield = £10,368 ÷ £213,450 = 4.86%.
Notice that net yield says nothing about whether you used a mortgage. It tells you what the asset itself produces relative to all-in cost.
Monthly cashflow: the survival metric
Monthly cashflow = Net monthly income − Monthly mortgage payment
Cashflow is what hits your bank account (before tax). It depends entirely on financing — same property at 75% LTV vs cash will have wildly different cashflow but identical yield.
For the property above, 75% LTV at 4.5% interest-only: loan £150,000, monthly interest = £562.50. Net monthly income = £10,368 ÷ 12 = £864. Monthly cashflow = £301. Comfortable.
Switch the rate to 5.5% (a 1-point rate rise, well within a refinance shock): monthly interest jumps to £687.50. Cashflow drops to £176. One unexpected boiler repair and you're negative for the month.
Why the two numbers diverge
Yield is fixed for a given property at a given price. Cashflow varies with:
- LTV (more leverage = lower cashflow but higher cash-on-cash return)
- Interest rate
- Whether you go interest-only or repayment
- Mortgage product fees amortised into the rate
Two investors looking at the same property, with different LTVs and rates, end up with the same yield but very different cashflow. One is comfortable; the other is exposed.
The trap of optimising one without the other
Yield-only thinking
“This property has a 7.5% net yield, that's great” → buys at high LTV → tiny cashflow → first void wipes out the year's profit. The yield is real; the survivability isn't.
Cashflow-only thinking
“I need £300/month cashflow” → buys cash-only → cashflow is great because there's no mortgage → yield is mediocre because the capital efficiency is poor → ten years later, the portfolio hasn't scaled.
How to use both, in order
For UK BTL, this is the right sequence:
- Filter by gross yield when scanning listings (5%+ filter is reasonable for most regions). Quick, dirty, sufficient at the top of the funnel.
- Calculate net yield on shortlisted deals to compare them on like-for-like asset productivity, independent of how you finance them.
- Calculate cashflow at your actual financing to confirm the deal will pay you each month. Test at multiple LTVs and rates.
- Stress-test the cashflow at +1-2% rate stress and -10% rent stress (see the stress-test guide). Surviving the stress test is what makes a deal safe in practice, not just on paper.
The shortcuts that get investors into trouble
- Using gross yield alone. Hides 25-35% of variation. Two properties with identical gross yield can have wildly different net yield depending on operating costs.
- Calculating yield against purchase price only, not total acquisition cost. Inflates the yield by 8-12% (the size of SDLT + fees relative to price).
- Forgetting interest-only ≠ profitable.Interest-only mortgages produce higher cashflow than repayment, but you're not building equity. The cashflow can be misleadingly attractive.
- Ignoring tax. Section 24 means individual landlords can no longer deduct mortgage interest from rental income as an expense — only a 20% basic-rate tax credit on finance costs applies. Your after-tax cashflow is materially below pre-tax, especially for higher-rate taxpayers (limited companies are unaffected). From April 2027 the basic-rate finance-cost credit rises to 22% to match the new 22% property basic rate — net cost similar, optics different.
Yield + cashflow + a third number
Serious UK BTL investors don't stop at two numbers. They also track:
- Cash-on-cash return — annual cashflow ÷ cash deployed (deposit + costs). Tells you the return on the money you actually put in.
- ICR (Interest Coverage Ratio) — for whether your lender will lend.
- Break-even mortgage rate — for whether the deal survives a rate cycle.
Together they cover productivity, sustainability, leverage efficiency, lending eligibility, and rate resilience. No single number tells you all five.
How PropQuant computes both, and connects them
Every deal in PropQuant shows net yield, gross yield, cash-on-cash, monthly cashflow, ICR, and break-even rate side-by-side. The verdict engine grades deals against your stored targets — so a deal that yields well but cashflows badly gets flagged as marginal, not strong, even if your yield target is met. Numbers without verdicts are easy to misread; the verdict forces you to consider both.
Frequently asked questions
What is net yield in UK BTL?
Net yield is annual net rental income (after operating costs but before mortgage) divided by the property's total acquisition cost (purchase price + SDLT + legal fees + survey + refurb), expressed as a percentage. It tells you the return the property generates on the money you put in, independent of leverage.
What's the difference between net yield and gross yield?
Gross yield uses gross rent (no costs deducted) divided by purchase price (no acquisition costs included). It's a quick screening number — good for filtering listings — but bad for comparing deals because it ignores 25-35% of cost variation. Always make decisions on net yield, not gross.
What is monthly cashflow on a BTL?
Monthly net rent (gross rent minus all operating costs) minus monthly mortgage payment. Positive cashflow means rent covers everything plus pays you a margin; negative means you're subsidising the property each month.
Can a deal have a great net yield but bad cashflow?
Yes — and it's common. A property at 7% net yield bought at 75% LTV with a 6% mortgage rate has the lender absorbing more than the rent generates. High yield, negative cashflow. Both numbers matter; checking only one is dangerous.
Which is more important?
Cashflow tells you whether the deal is sustainable month-to-month. Yield tells you whether the asset is fundamentally productive. You need positive cashflow to survive; you need decent yield to grow. A high-yield deal with marginal cashflow is acceptable; a low-yield deal with positive cashflow only works if you have a clear capital growth thesis.
What's a 'good' net yield in the UK?
Region-dependent. South-East/London: 4-5% is typical. Midlands/North: 6-8% is achievable. HMO and SA strategies push 8-12%+. A 'strong' net yield is one that exceeds your specific target — set a target you'd actually walk away from a deal for.
What's a 'good' monthly cashflow?
Set against your costs of capital and risk. £150-300/month after all costs is a common floor for UK BTL investors — enough to absorb a void or a one-off repair without becoming a problem.