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Void periods explained (UK landlords): how to budget and stress-test your numbers

A practical UK landlord guide to void periods: what they are, how they affect cash flow, and how to stress-test rental yield and mortgage costs with worked examples.

Published: 10/04/2026 • Last verified: 10/04/2026

Summary

A void period is time when your rental property is not producing rent — usually because it’s empty between tenants. Voids matter because many costs don’t stop just because rent does.

The practical way to handle void risk is to model your numbers in annual terms:

  • reduce annual rent for the void time you want to stress test
  • keep the “always-on” costs running (mortgage, insurance, service charges)
  • add realistic changeover costs (letting fees, safety checks, refresh work)

Then re-run your numbers in the yield calculator.

Key terms (quick definitions)

  • Void period: time without a tenant (and usually without rent).
  • Gross yield: rent before costs, as a percentage of property value.
  • Net yield: rent after costs, as a percentage of property value.

How it works

1) Start with annual rent, not monthly rent

Monthly rent is useful for cash flow, but it can hide void risk. Annual rent makes it easy to incorporate vacancy:

[ \text{Effective annual rent} = \text{monthly rent} × (12 - \text{void months}) ]

If you prefer weeks:

[ \text{Effective annual rent} = \text{weekly rent} × (52 - \text{void weeks}) ]

2) Split your costs into “always on” vs “changeover”

Always-on costs (often continue during voids):

  • mortgage payments (or interest-only payments)
  • buildings insurance
  • service charges / ground rent (if leasehold)

Changeover costs (often happen when tenants change):

  • letting/management fees
  • safety checks (depending on your setup and timing)
  • cleaning, redecorating, minor repairs

3) Stress test, don’t “best-case”

If you run your model with 0% voids and no maintenance, you’re not doing a test — you’re doing a best-case scenario.

A stress test doesn’t need to be perfect. It needs to be honest and repeatable. For many landlords, “one month void per year” is a simple starting scenario.

Void periods aren’t just a yield issue — they can affect whether you can keep paying the mortgage.

If you’re using the buy-to-let mortgage calculator, stress test affordability using a lower effective rent (for example, rent reduced by one month per year) and see how the result changes.

Worked examples

These examples are simplified for budgeting and education.

Example 1: One month void per year

  • Monthly rent (when let): £1,200
  • Planned voids: 1 month/year

Effective annual rent:

[ £1,200 × 11 = £13,200 ]

If you previously budgeted using £1,200 × 12 = £14,400, the “void-adjusted” rent is £1,200 less per year.

Takeaway: a single month of voids is the same as losing one full month’s rent — and you may still have costs.

Example 2: Two-week void + letting fee + refresh

  • Weekly rent: £275
  • Void: 2 weeks
  • Letting cost (illustrative): 1 week rent
  • Refresh cost (illustrative): £400

Rent lost to void:

[ £275 × 2 = £550 ]

Letting cost:

[ £275 ]

Total impact before refresh:

£550 + £275 = £825, plus the £400 refresh = £1,225 total.

Takeaway: the “void cost” is often more than just the missing rent.

Example 3: Stress test monthly cash flow

Assume:

  • Monthly rent when let: £1,100
  • Mortgage payment (interest-only, illustrative): £850
  • Insurance + service charges (illustrative): £120
  • Planned voids: 1 month/year

In 11 “let” months, the monthly cash flow is:

£1,100 − £850 − £120 = £130

In the void month, the cash flow is:

£0 − £850 − £120 = −£970

Annualised, the “good months” (11 × £130 = £1,430) don’t fully offset the void month (−£970) plus any changeover costs.

Takeaway: if you only look at “let months”, you can underestimate the buffer you need.

Common mistakes

  • Treating voids as “rare” without modelling them.
  • Ignoring costs that continue during voids (mortgage, insurance, service charges).
  • Confusing voids (empty property) with arrears (unpaid rent).
  • Using gross yield and forgetting management/maintenance/void allowance.
  • Forgetting changeover costs (letting fees, safety checks, refresh work).
  • Not running at least one conservative scenario (for example, one month void per year).
  • Assuming all costs are tax-deductible without checking HMRC guidance.

What to do next

FAQ
Is a void period the same as arrears?
No. A void period usually means the property is empty and no rent is due because there is no tenant. Arrears means rent is due under a tenancy but hasn’t been paid.
How should I model voids in my yield calculation?
A simple approach is to reduce your annual rent by the number of void weeks you want to stress test (for example, one month). Then re-run your yield with the lower annual rent.
Do I still have costs during a void?
Often yes. Mortgage payments, insurance and service charges can continue. You may also have letting fees, safety checks and repair/refresh costs.
What’s a sensible stress test if I don’t know what voids to expect?
Many landlords start with a conservative scenario (for example, one month of voids per year) and check that the numbers still work. The right stress test depends on the local market, tenant type and your own cash buffer.
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