— Free UK Property Tool —

Property Flip Profit Calculator

Full deal analysis in one tool — gross and net profit, ROI on cash, annualised return, 70% rule check, break-even ARV. Includes bridging finance, refurb contingency, SDLT additional property surcharge, and CGT vs Income Tax modelling. Compare your flip returns against a BTL on the same property.

70% Rule Check Bridging Finance Refurb Contingency Annualised ROI CGT vs Income Tax Break-Even ARV
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Deal Details

Purchase
Purchase Price£
£
Cash purchase
No bridging finance — uses 100% equity
Bridging LTV% of purchase financed
%
Bridging Rate (annual)BTL bridging avg 9–12%
%
Refurbishment
Refurb Budgetkitchen, bathroom, decoration
£
Contingency% of refurb — recommended 15%
%
Holding Periodpurchase to sale completion
mo
Sale
After-Repair Value (ARV)estimated final sale price
£
Selling Agent Fee% of sale, +VAT
%
Solicitor (Sale)typical £1,200–2,000
£
EPC + Other Selling Costs£
£
Tax
Income Tax Band
Use CGT instead of Income Tax
CGT for long holds (12m+). Income Tax for trading flips.
↓ Methodology ↓
How this calculator works — formulas & sources
The 70% Rule
Max Purchase Price = (ARV × 70%) − Refurbishment Costs
ARV = After-Repair Value (estimated post-renovation sale price)
The 70% rule is a quick deal screening threshold. The 30% buffer must cover SDLT, bridging finance, legal fees on both sides, agent commission on sale, and your profit margin. Below the 70% threshold the deal has room to work; above it, risk increases significantly. When a deal fails the 70% rule, model it as a BTL hold instead. Stamp Duty (SDLT) explained · HMO vs BTL
SDLT on Flip Purchase
SDLT = Banded calculation with 5% BTL surcharge across all bands
5% on £0–125k · 7% on £125–250k · 10% on £250–925k
All flip purchases attract the additional property surcharge — there is no exemption for short-term holds or development intent. SDLT is paid on purchase and cannot be reclaimed on sale. Use the SDLT calculator for the exact banded calculation. Stamp Duty (SDLT) explained · Section 24 explained
Bridging Finance Cost
Bridging Cost = Loan × Monthly Rate × Hold Period (months)
Loan = Purchase Price − Deposit
Arrangement Fee = Loan × Arrangement % (typically 1–2%)
Bridging interest compounds monthly. The calculator uses simple interest for transparency. Total bridging cost includes arrangement fee plus monthly interest for the full hold period. The SDLT surcharge is paid at purchase on top of bridging costs. Stamp Duty (SDLT) explained
Net Profit
Gross Profit = Sale Price − Purchase Price − Refurb − All Costs
All Costs = SDLT + Bridging + Legal (buy) + Legal (sell) + Agent Fee
Net Profit = Gross Profit − Tax
Refurbishment contingency (default 10%) is added to the refurb budget automatically. Agent commission applies to the full sale price. Legal fees are estimated for both purchase and sale transactions. If net profit is thin, model the same property as a BTL or HMO hold post-refurb. HMO vs BTL
CGT vs Income Tax
CGT (long holds 12m+): 18% basic / 24% higher rate
Income Tax (trading): up to 45% at additional rate
Annual CGT exempt amount: £3,000 (from April 2024)
HMRC determines classification based on activity pattern. Regular flippers using bridging finance for short-term holds are typically treated as traders — taxed at Income Tax rates. Hold 12+ months with clear investment intent and CGT may apply. Unlike BTL landlords, traders cannot claim Section 24 credits but also don't face the same restrictions. Always confirm with a specialist accountant. Section 24 explained · HMO vs BTL
Annualised ROI
ROI = Net Profit ÷ Total Cash Invested × 100%
Annualised ROI = (1 + ROI)^(12 ÷ Hold Months) − 1
Total Cash Invested = Deposit + SDLT + Legal + Refurb
Annualised ROI allows fair comparison between flips of different durations. A 15% return on a 3-month flip annualises to 74% — far stronger than a 25% return on an 18-month project at 18% annualised. Compare against BTL cash-on-cash ROI to decide which strategy suits the property. HMO vs BTL
Sources: HMRC SDLT guidance (October 2024 rates) · HMRC Capital Gains Tax rates (April 2024) · Finance Act 2003 (SDLT) · HMRC Business Income Manual BIM60000 (property trading)
Last reviewed: April 2026

Deal Results

Net Profit (after tax)
—
—
⬤ Calculating…
Returns
ROI on Cash
—
return on deposit
Annualised ROI
—
scaled to 12 months
Profit Margin
—
% of ARV
Cash Invested
—
total deployed
70% Rule Check
70% Rule —
—
Cost Breakdown
Break-Even Analysis
Break-Even ARV—
Margin of Safety—
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How it works

What makes a flip work

Property flipping is profitable only when the numbers work before you buy. Here's what each metric tells you and where flips usually fail.

THE 70% RULE
The investor’s safety net

The 30% buffer covers SDLT, bridging interest, agent fees, solicitor and survey, holding costs, and the profit margin you actually need to make. Pay more than this and the deal is too tight to absorb mistakes. Cash buyers can stretch to 75%; novice flippers should stick to 65%. If flipping doesn’t stack up, a BTL hold on the same property might. Stamp Duty (SDLT) explained · HMO vs BTL

INCOME TAX vs CGT
HMRC chooses, not you

If HMRC views your activity as trading (regular flips, finance structured for short hold, intent to sell), you pay full Income Tax — up to 45%. Genuine investment held over a year may qualify for CGT (18%/24%). Frequency, finance type, and intent all matter. The tax difference can be £20,000+ on a single deal. Unlike BTL landlords, flippers don’t face Section 24 — but trading classification means no CGT rates either. Section 24 explained · HMO vs BTL

BRIDGING FINANCE
The hidden profit killer

Bridging loans run at 9–12% annually plus 2% arrangement fees and 1% exit fees. On a £100k loan over 6 months, that’s £5,000 in interest plus £3,000 in fees — £8,000 gone before you sell. Cash buyers skip all of this, which is why cash deals can stretch the 70% rule to 75%. Don’t forget the SDLT surcharge is on top of all of this. Stamp Duty (SDLT) explained

SDLT SURCHARGE
5% on the entire purchase

All flip purchases trigger the 5% additional property SDLT surcharge (since October 2024) because you already have or will have another property. On a £150k purchase that’s £8,000 in stamp duty alone. There is no “I’ll sell within 6 months” exemption — you pay it on completion. Use the SDLT calculator to get the exact banded figure for your purchase price. Stamp Duty (SDLT) explained

REFURB CONTINGENCY
Always 15% minimum

Property renovation costs overrun. Always. Damp behind the wall, electrics needing rewiring, hidden structural work — these get found mid-project. A 15% contingency on a £30k refurb is £4,500. First-time flippers should use 25%. If refurb costs make the flip unviable, the same property let as a BTL or HMO post-refurb is worth modelling. HMO vs BTL

ANNUALISED ROI
The honest comparison metric

A 20% return on a 6-month flip is far better than 25% on an 18-month one. Annualised ROI scales the return to a 12-month basis so you can compare flips with different timelines. Strong flippers hit 30%+ annualised consistently — well above typical BTL cash-on-cash returns. HMO vs BTL

FAQ

Common questions

What is the 70% rule in property flipping?
The 70% rule says your maximum purchase price should be 70% of the After-Repair Value (ARV) minus your refurbishment costs. The 30% buffer covers all transaction costs (SDLT, bridging, agent fees, solicitor, holding) plus the profit margin you actually need. Example: if ARV is £250,000 and refurb is £25,000, your maximum offer is £150,000. Pay more and the deal is too tight to absorb the inevitable surprises in renovation timing, costs, or final sale price. Stamp Duty (SDLT) explained · HMO vs BTL
Will HMRC tax my flip as Income Tax or Capital Gains Tax?
HMRC determines this based on activity, not your preference. If you flip property regularly (more than once or twice), use bridging finance designed for short-term holds, or buy with clear intent to sell quickly, HMRC will treat you as trading — taxed at full Income Tax rates (up to 45% plus National Insurance). Genuine long-term investments held 12 months+ with rental income may qualify for CGT (18% basic / 24% higher rate from April 2024) with a £3,000 annual exemption. The tax difference can exceed £20,000 on a single deal. Unlike BTL landlords who face Section 24 on mortgage interest, flippers classified as traders pay tax on the full profit — no interest restriction credit. Always consult an accountant before your first flip. Section 24 explained · HMO vs BTL
How much SDLT do I pay on a flip purchase?
All flip purchases pay the additional property SDLT surcharge: 5% on the first £125k, 7% on £125k–250k, 10% on £250k–925k, and so on. There is no exemption for short-term holds or "intended to sell" purchases. On a £150,000 flip purchase, SDLT is £8,000. On a £250,000 flip, it's £15,000. This is paid on completion and must be factored into your 70% rule calculation. The surcharge increased from 3% to 5% in October 2024. Stamp Duty (SDLT) explained
What does "annualised ROI" actually mean?
Annualised ROI scales your return to a 12-month basis so you can compare flips with different timelines. A 20% return on a 6-month flip annualises to 44% — much stronger than a 25% return on an 18-month flip which annualises to only 16%. This is the metric experienced flippers focus on because it captures the velocity of your capital. Strong flippers hit 30–40%+ annualised consistently. Below 15% annualised, the risk usually doesn't justify the work.
How accurate is the bridging finance calculation?
The calculator uses interest-only bridging at the rate you specify, plus a typical 2% arrangement fee and 1% exit fee (3% total). Real-world variations: some lenders charge interest in advance (rolled up), some defer it until exit; arrangement fees vary 1.5–3%; exit fees can be 0–2%. The calculation here represents a typical mid-market bridging deal. For exact figures, get an Agreement in Principle from a bridging specialist before committing to a purchase. Don’t forget the SDLT surcharge sits on top of all bridging costs in your total cash required. Lenders vary significantly on rates and fees — always get multiple quotes. Stamp Duty (SDLT) explained · HMO vs BTL · Rent vs Buy explained
What's a realistic profit margin on a flip?
After all costs and tax, target a net profit margin of 10–15% of the ARV. Below 8%, the risk-reward is too tight — any small overrun on refurb or undershoot on sale price wipes the profit. Above 15% margin and the deal is genuinely strong. The £25–40k net profit range is typical for £150–250k flips when the numbers work. Below £15k net, most experienced investors walk away — or convert the acquisition into a BTL or HMO hold instead. HMO vs BTL