Rental payback can look attractive, but the tax and regulatory treatment is not settled for detached auxiliary dwellings. Any calculator on this site is illustrative only and not tax advice.
Start with gross rent, then subtract realistic annual costs before thinking about tax: insurance differences, repairs, maintenance, utilities, cleaning between long-term tenancies, compliance checks, financing, and possible property-related charges.
If future law allows a specific relief, the calculation may change. If it does not, taxable rental income and other obligations may materially change the payback period.
We deliberately do not model short-stay platform income as the default path. Current Rent-a-Room guidance excludes short-term guests and online booking style leisure stays.
Payback variables to include
A realistic payback check should start with total installed cost, not the unit price alone. Include foundations, service connections, wastewater, access works, professional fees, compliance, furnishing, contingency and VAT assumptions. Then compare that against conservative long-term rental income, not best-case short-stay income.
| Variable | Why it changes payback |
|---|---|
| Tax treatment | Detached units do not currently qualify under published Rent-a-Room guidance. |
| Vacancy | Even strong rental areas can have empty periods, repairs or tenant changes. |
| Utilities | Separate metering may not be available or cost-effective. |
| Insurance | A rental use can change cover, conditions and premium. |
| Maintenance | Heating, ventilation, bathroom, roof, doors and appliances need a reserve. |
Conservative example logic
If a project costs EUR90,000 installed and produces EUR1,200 per month gross, the simple payback looks short. Once tax, maintenance, insurance, utilities, vacancy and finance are included, the practical payback can be much longer. That does not make the project bad; it means the decision should be made with net income and risk in mind.
Planning and tenant-use caution
Rental use can be viewed differently from family use. A unit intended for a tenant may raise questions around independent occupation, access, parking, services, fire safety, private open space and long-term compliance. Before relying on rental income, confirm both the planning and tax position for the actual site.
Use the calculator as a screening tool only. A quote, planning check and tax view should come before any deposit based on expected rent.