Void Period Cost Calculator — What an Empty Rental Really Costs
Add up council tax, mortgage interest, insurance, utilities and re-let costs over a void, see the cost per week and per year, and the break-even rent cut that would make it worth avoiding.
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A void isn’t just lost rent. Council tax, insurance, utilities and (if there is one) mortgage interest all keep running while a property sits empty, and re-letting itself costs money — an agent’s tenant-find fee, referencing, a clean and some marketing photos. This calculator adds all of that up for the length of void you enter, and turns the total into a cost per week, a share of the year’s rent, and a break-even rent cut — the most a landlord could shave off the rent, and still come out even, if a slightly cheaper price let the property immediately instead.
How the total is worked out
Monthly running costs (mortgage interest, insurance, utilities) are converted to a weekly rate the same way rent is converted elsewhere on this site — monthly × 12 ÷ 52, because a year has about 52.14 weeks, not 48. Council tax is entered as an annual figure and divided by 52 directly. Those weekly figures are multiplied by the number of void weeks and added to the one-off re-let costs (agent fee, referencing, cleaning) to give the total.
Typical void lengths (Goodlord Rental Index)
How long a property actually sits empty varies a lot by area. The Goodlord Rental Index’s regional void-period table — days between tenancies, shortest first — reads: Greater London 15, North East 17, South West 18, South East 19, North West 20, East of England 21, East Midlands 22, Yorkshire and the Humber 22, West Midlands 23. The national average across the table is 19 days. The three preset buttons above use the shortest region (Greater London), the national average, and the longest region (West Midlands) from that table, converted to weeks. If you know your own area’s typical void — from a letting agent, or your own history with the property — type it in directly instead; the presets are a starting point, not a forecast.
The break-even rent cut, explained
The break-even figure answers a specific question: if accepting a lower rent let the property immediately instead of sitting empty for this long, how much lower could that rent be before the landlord is worse off overall? It spreads the void’s total cost over a full year (total ÷ 12) — the monthly rent cut that, sustained for twelve months, costs exactly as much as this one void. It works out to the same percentage as the void’s share of annual rent, because both are just the same total cost measured two different ways: once against a year of rent collected in full, once against twelve months of a slightly discounted rent instead.
What stays deductible
None of this is wasted for tax purposes. Council tax, insurance, utility standing charges and the re-let costs above are allowable expenses against rental income for as long as the property is genuinely being marketed to re-let — HMRC does not require a tenant in place, only a continuing intention to let. Mortgage interest is treated differently: since 2020 it is not deducted directly, it earns the Section 24 credit (20% of the interest, reducing the tax bill rather than the taxable profit) — still valuable, just calculated differently. The full breakdown, with a worked example, is on the council tax and utilities during void periods page.
Where this fits with the rest of the numbers
A void is one of the running costs a rental yield calculator should already allow for — if you built your yield on 52 weeks of rent a year, this calculator shows how far that overstates a real year. If a lower rent is genuinely on the table to cut the void, check it still clears referencing with the rent affordability calculator before offering it. And the ordinary running costs here — agent fees, insurance, general upkeep — are covered in full on the allowable expenses list and the letting agent fees page.
Void-period regional table: Goodlord Rental Index, “Void periods averaging three weeks throughout England and Wales”, published 7 March 2025 (blog.goodlord.co/void-period); Goodlord’s live Rental Index tracker was showing a methodology-update notice (due back 1 October 2026) when checked 13 September 2026, so this is the most recent complete regional breakdown available — enter your own local figure if you have one. England average council tax: MHCLG, “Council Tax levels set by local authorities in England 2026 to 2027”, Table 9, published 25 March 2026, mean of 296 billing authorities, read 13 September 2026. Tax treatment: HMRC PIM2010/PIM2510 and ITTOIA s.272A–274A (Section 24), as used throughout this site’s tax calculators. General information, not advice — check your own council’s empty-property rules and your policy documents for exact figures.
Asked constantly
Yes, in almost all cases. Most councils removed the old empty-property discount years ago, so the bill is usually the landlord's from day one of the void, at the full Band charge (some still give a short discount — check with your own council). It remains an allowable expense while you intend to re-let.
No. Council tax, insurance, utilities and re-let costs are deducted from rental income in full. Mortgage interest is a finance cost, so instead of a deduction it earns the Section 24 credit — 20% of the interest, taken off the tax bill rather than the taxable profit.
The Goodlord Rental Index's regional table (7 March 2025) ranges from 15 days in Greater London to 23 days in the West Midlands, with a 19-day national average — call it two to three and a half weeks. Individual 2026 monthly reports have shown national averages anywhere from the low teens to the mid-20s depending on the season, so a local letting agent's current estimate is worth more than any single national figure.
It's the most you could lower the rent by, kept for a full year, that would cost the same as this one void. If a lower asking rent would genuinely let the property straight away, cutting by less than this figure still leaves you better off than enduring the void; cutting by more does not.
Yes — tenant-find fees, referencing and credit checks, and cleaning or redecoration between tenants are all allowable expenses, the same as council tax and utilities during the void. See the allowable expenses list for the full set.
Doing this every quarter, not just once?
Keep the same figures all year instead of re-typing them: rent and expenses per property, the Section 24 finance costs and the MTD quarterly totals, in one workbook.
Landlord Tax Lab stays free. We also sell the Landlord Tax Pack: one Excel workbook for up to 10 properties that logs rent and expenses per property, maps every line to its SA105 box, keeps Section 24 finance costs out of the expense boxes, and rolls up the MTD quarterly totals. £19 once — no subscription.
Disclosure: we make and sell the Tax Pack — this is our own product, not a paid recommendation. It does not file anything with HMRC and it is not tax advice; filing goes through you, your accountant or software on HMRC’s compatible-software list.