Tool

UK BTL Cash Flow Modeler

Project the real cash flow on a UK buy-to-let. Models mortgage interest, Section 24 tax credit, council tax voids, letting agent fees, service charges and rent growth over 1-30 years.

Section 24 — Why UK BTL Tax Hurts

Since April 2020, mortgage interest is NOT a deductible expense for individual UK landlords. Instead you get a flat 20% tax credit on interest paid. If you are a higher-rate (40%) or additional-rate (45%) taxpayer, this means you are effectively taxed on revenue you never saw. This model calculates tax the correct post-Section 24 way.

Property & Mortgage

Property Price

Deposit

Mortgage Rate (5yr fix)

Mortgage Term

yrs

Interest-only mortgage

Rent & Running Costs

Gross Monthly Rent

Council Tax Band (paid during voids)

Landlord Insurance

% of value

Letting Agent Management

% of rent

Maintenance Reserve

% of value

Vacancy Rate

% (8% ≈ 1 mo/yr)

Service Charge + Ground Rent

£/mo

Growth & Tax

Annual Rent Growth

Annual House Price Appreciation

Income Tax Bracket

Projection: 15 years

Higher Rate (40%)

⚠ At least one projection year has negative cash flow. Check the year-by-year table below.

Monthly Net Cash Flow (Y1)

£-126

Annual Net Cash Flow (Y1)

£-1,514

Gross Yield

6.11%

Net Yield (after all costs, Y1)

-0.55%

Annualised ROI on Cash

-2.04%

Break-Even Year

Never in period

Cash Flow Projection — 15 years

Year-by-Year Breakdown

Year	Effective Rent	Mortgage Interest	Op. Expenses	S24 Credit	Tax Due	Net CF	Cum. CF	Property Value
1	£15,456	£9,281	£5,604	−£1,856	£2,085	£-1,514	£-1,514	£283,250
2	£15,920	£9,281	£5,767	−£1,856	£2,205	£-1,333	£-2,847	£291,748
3	£16,397	£9,281	£5,935	−£1,856	£2,329	£-1,148	£-3,995	£300,500
4	£16,889	£9,281	£6,108	−£1,856	£2,456	£-956	£-4,951	£309,515
5	£17,396	£9,281	£6,286	−£1,856	£2,588	£-759	£-5,710	£318,800
6	£17,918	£9,281	£6,469	−£1,856	£2,723	£-556	£-6,265	£328,364
7	£18,455	£9,281	£6,658	−£1,856	£2,863	£-346	£-6,612	£338,215
8	£19,009	£9,281	£6,852	−£1,856	£3,006	£-131	£-6,743	£348,362
9	£19,579	£9,281	£7,053	−£1,856	£3,154	£91	£-6,652	£358,813
10	£20,167	£9,281	£7,259	−£1,856	£3,307	£320	£-6,332	£369,577
11	£20,772	£9,281	£7,471	−£1,856	£3,464	£555	£-5,777	£380,664
12	£21,395	£9,281	£7,690	−£1,856	£3,625	£798	£-4,980	£392,084
13	£22,037	£9,281	£7,916	−£1,856	£3,792	£1,047	£-3,932	£403,847
14	£22,698	£9,281	£8,148	−£1,856	£3,964	£1,305	£-2,628	£415,962
15	£23,379	£9,281	£8,387	−£1,856	£4,140	£1,570	£-1,058	£428,441

Deposit

£68,750

Loan Amount

£206,250

Monthly Mortgage

£773