A £50-a-month rent increase looks, on paper, like straightforward extra income — £600 a year, no cost, no effort. It’s only straightforward if the tenant stays. If it’s the push that sends a good tenant looking elsewhere, the arithmetic changes completely, and not in the landlord’s favour. Understanding when maximising the rent actually maximises your return, and when it doesn’t, is a genuinely useful piece of property judgement — one that gets skipped surprisingly often in favour of a simpler, less accurate instinct: “get what the market will bear.”
What a void period actually costs, in real current figures
The latest analysis from Rushbrook & Rathbone put the average rental void period across England at 21 days in June 2026, down from 24 days in May but still two days longer than in June 2025. See the latest void-period research.
An earlier cost analysis from the same firm, published in June, had used the then 24-day average void period and an average monthly rent of £1,438 to estimate £1,135 in lost rental income per void, 12.9% higher than the equivalent figure a year earlier. That study found meaningful regional variation: London’s void periods were among the shortest, at around 16.6 days, but its estimated cost per void was the highest in the country at roughly £1,252 because rents were substantially higher; the West Midlands saw the sharpest year-on-year increase in estimated void costs, at 52.9%. See the earlier void-cost analysis.
Those figures are industry research rather than an official national measure, and the later fall from 24 to 21 days is a useful reminder not to treat £1,135 as a universal or permanent “average void cost”. The real figure for an individual landlord depends on the property’s rent, how long it actually sits empty and what costs arise around the change of tenancy.
And that’s before the costs beyond lost rent even enter the picture. A realistic full accounting needs to distinguish turnover costs caused by changing tenant from carrying costs that continue while the property produces no rent.
Continued mortgage payments, insurance, service charges and utility standing charges aren’t necessarily costs created by the void — most would exist with a tenant in place too — but during an empty period they still need paying without rental income to offset them. Council Tax can matter as well: in England, an owner will usually have to pay Council Tax on an empty property, although councils can offer discounts and exemptions apply in some circumstances. The government’s guidance on Council Tax for empty properties explains the basic position.
Turnover-specific costs can include a letting agent’s re-letting or tenant-find fee if one’s used; advertising costs if self-managing; a fresh inventory and check-in process; cleaning and often some redecoration between tenancies; and minor repairs that tend to surface specifically at a change of occupancy. Compliance work may also happen to fall due around the same time, although something that would have been required anyway shouldn’t automatically be counted as a cost caused by the void.
Then there’s the less tangible but genuinely real time cost of managing the whole process and the uncertainty of who the replacement tenant will actually turn out to be.
Not every turnover incurs every one of these costs — a straightforward change between two well-referenced tenants in a property in good condition is a lighter event than a turnover following a difficult tenancy — but a realistic estimate needs to account for more than just the empty weeks of rent.
Working through the actual trade-off
Take a genuinely illustrative example, using round numbers rather than a specific claim about any particular property. A landlord is charging £1,200 a month and considers raising it to £1,250 — a modest, defensible £50 increase, £600 a year if the tenant simply pays it and stays.
But suppose that increase is enough to prompt the tenant to start looking elsewhere, and the property ends up empty for three weeks during the search for a replacement: that’s roughly £830 in lost rent alone, before any of the additional turnover costs above are even added. A six-week void, not unrealistic depending on the property and market, is closer to £1,660 in lost rent alone.
The particularly useful number here is the break-even point.
At £1,200 a month, the property generates about £39.45 a day in rent across a year. The entire £600 annual benefit of the £50 increase is therefore wiped out by just over 15 empty days.
| Empty period | Approximate lost rent at £1,200 a month | Compared with the £600 annual gain |
|---|---|---|
| 7 days | £276 | Increase still ahead by £324 before other costs |
| 15 days | £592 | Almost the entire annual gain gone |
| 21 days | £828 | £228 more lost than the annual gain |
| 42 days | £1,657 | More than £1,000 beyond the annual gain |
And that table still assumes no cleaning, re-letting, inventory, advertising or other turnover costs at all.
A simple way to run this on your own property is:
Break-even empty days = annual value of the proposed rent increase ÷ current daily rent
Set against a £600 annual gain from the increase, the maths only works straightforwardly in the landlord’s favour if the tenant stays and pays the higher rent, or if any resulting turnover is short and inexpensive enough that the higher rent recovers the loss reasonably quickly. The moment a marginal increase triggers a meaningful void plus turnover costs, it can take a surprisingly long time to earn the money back.
This isn’t an argument that rent increases inevitably cause tenants to leave — they don’t. A fair, well-communicated increase that reflects genuine market movement can be a normal, reasonable part of running a rental property. It’s an argument for actually running this calculation before assuming an increase is automatically free money, particularly where the increase is large relative to the tenant’s existing rent, or where the local market for re-letting quickly is genuinely uncertain.
There is also a practical legal backdrop in England. For most assured periodic tenancies, rent cannot normally be increased during the first year and can then generally be increased only once every 12 months through the formal Section 13 process, using Form 4A and giving at least two months’ notice. Government guidance recommends discussing the increase with the tenant before serving the formal notice. See the current rent-increase rules for landlords.
That doesn’t decide whether an increase is commercially sensible. It does make the point at which you consider one a particularly sensible moment to run the economics properly.
When pursuing market rent is still the right call
None of this means below-market rent should be preserved indefinitely out of loyalty or inertia — that’s its own mistake, just in the opposite direction. Pursuing market rent makes clear sense where the gap between current and market rent has become substantial rather than marginal, where local demand is strong enough that re-letting quickly at the new figure is genuinely likely if the current tenant does leave, where a landlord has a genuine, non-negotiable financial need for the additional income, or where significant works are already planned around a genuine change of tenancy, making the timing less costly than it would otherwise be.
The judgement isn’t “never increase rent to protect a tenant” — it’s weighing the size of the gap to market, the realistic likelihood and cost of a resulting void, and what you actually need the property to generate, rather than defaulting to either extreme.
There is a meaningful difference, for example, between keeping a reliable tenant at £1,200 when the genuinely evidenced local market is £1,225 and keeping the same tenant at £1,200 when comparable properties are consistently letting at £1,500. The first is a relatively small price for stability; the second may represent enough foregone income to justify a very different decision.
What a genuinely good tenant is actually worth
“A good tenant is worth their weight in gold” is the kind of phrase that sounds true and explains nothing. What it actually cashes out to, in concrete terms: reliable, on-time rent, month after month, without the management time and stress of chasing late payments; potentially fewer disputes, because an established tenant who communicates well can raise issues early rather than allowing them to become larger problems; a known, demonstrated pattern of how the property’s actually treated, rather than the unknown risk that comes with every new tenancy; stable occupancy, which compounds in value the longer it continues, because every year without a turnover is a year without void costs, re-letting fees and re-referencing; and, harder to quantify but genuinely real, a lower ongoing management burden simply because an established tenancy with a reliable tenant creates less uncertainty.
That doesn’t mean an existing tenant should be treated as irreplaceable. It means certainty itself has a value, even though it never appears as a separate line on a rental statement.
A newly referenced applicant may look excellent on paper and go on to be an excellent tenant. But until the tenancy has actually run for a period of time, they’re still an unknown quantity in a way that a proven tenant simply isn’t.
Thinking about this as an investment metric, briefly
For a landlord tracking the real performance of a property, the useful figure isn’t the headline rent achievable if the property were permanently occupied at the top rate — it’s rent actually collected across the year, accounting for any void periods and the costs that come with them.
A property let at a slightly below-market rent but occupied continuously for three years can genuinely outperform, in total collected income, a property chasing top rent but sitting empty between shorter tenancies — the arithmetic depends entirely on the specific numbers, but the principle is worth holding onto: occupied-at-a-discount can beat empty-at-full-price, once every real cost of the empty period is properly counted rather than ignored.
One useful way of thinking about this is effective annual rent rather than advertised monthly rent.
A property at £1,250 a month occupied for all 12 months produces £15,000 in gross rent.
A property at £1,300 a month but empty for one full month produces £14,300.
The apparently “better” monthly rent has produced £700 less rent over the year, before any turnover costs are counted.
This article focuses specifically on the tenancy-management economics of that trade-off; the fuller picture of yields, return on capital and broader investment appraisal belongs in our Market & Money section, under Property Investment.
The judgement, not the rule
There’s no universal answer here, and “never lose a good tenant” is exactly as unhelpful as “always charge full market rent.”
What’s actually useful is running the real numbers for your specific situation before deciding: how large is the gap to market rent, genuinely, and how confident are you in quickly re-letting at the higher figure if this tenant does leave? What would a realistic void, with realistic turnover costs, actually cost you against the gain you’re chasing? And separately from the pure arithmetic — what is a proven, reliable tenant actually worth to you in reduced management burden and certainty, beyond what any spreadsheet captures?
A useful decision therefore comes down to four questions:
- What will the proposed increase actually add over 12 months?
- How many empty days would wipe that gain out?
- What genuine turnover costs would arise if the tenant left?
- How large is the gap between the current rent and properly evidenced local market rent?
Sometimes maximum theoretical rent is genuinely the right call. Often, once the full cost of turnover is honestly counted rather than assumed away, it isn’t — and the only way to know which situation you’re actually in is to do the sum before deciding, rather than after.
This article uses current England rental-market data and illustrative worked examples for general guidance and does not constitute financial or investment advice. Void periods, turnover costs and market conditions vary substantially by region and property type. Rent-increase rules also differ elsewhere in the UK, so the England-specific legal process cited above should not be assumed to apply in Scotland, Wales or Northern Ireland.
