If you are a landlord in Cardiff with a modest portfolio of two or three properties in areas like Roath, Canton, or Heath, there is a significant tax deadline heading your way that you may not yet be aware of. Making Tax Digital for Income Tax Self Assessment (MTD for ITSA) expanded on 6 April 2026 to include those with gross property income above £50,000. But the next phase — arriving on 6 April 2027 — lowers that threshold to £30,000, and it will pull a considerable wave of Cardiff landlords into scope for the first time.
At Martin & Co Cardiff, we believe in empowering landlords with the information they need, well ahead of any deadline. This guide is here to help you understand exactly what is changing, whether it applies to you, and what steps you should be taking right now.
Why the April 2027 threshold matters for Cardiff landlords
The £30,000 gross income threshold is not a figure that only affects large-scale portfolio landlords. In Cardiff’s current rental market, it is a level that can be reached with a surprisingly modest number of properties.
Average monthly rents across key Cardiff postcodes currently range from approximately £1,068 in parts of CF24 (Roath) to around £1,450 per month in sought-after areas of CF14 (Heath) and CF5 (Canton). A landlord with just two mid-range properties in these neighbourhoods could generate gross rental income of between £25,600 and £34,800 per year — placing them either close to or comfortably above the £30,000 threshold.
HMO landlords in Cathays
The picture is even more acute for HMO landlords operating in Cathays (CF24), a neighbourhood with consistently strong demand driven by Cardiff University’s large student population. A well-occupied five-room HMO generating between £575 and £725 per room per month produces gross annual income of between £34,500 and £43,500 from a single property alone — well above the incoming £30,000 threshold.
Even a single fully-occupied HMO in Cathays could bring a landlord into MTD scope from April 2027. If that applies to you, the time to prepare is now — not next spring.
How gross income is calculated under MTD
One of the most important things to understand is that MTD for ITSA is based on gross rental income — that is, your total rental receipts before any expenses are deducted.
This means mortgage interest, letting agent fees, maintenance costs, insurance premiums, and any other allowable deductions do not reduce the figure used to determine whether you are in scope. If your contract holders pay you a combined total of £30,000 or more in rent during a tax year, you will be required to comply — regardless of what your net profit looks like after costs.
This is a detail that catches many landlords off guard, and it is one of the reasons Martin & Co Cardiff encourages all landlords to review their income position now, rather than waiting until the threshold has already been crossed.
What MTD for ITSA actually requires you to do
Once you are in scope, the requirements change significantly compared to the traditional annual Self Assessment tax return. Here is what you will need to do:
Quarterly updates to HMRC
You will be required to submit a summary of your income and expenses to HMRC four times per year, using HMRC-compatible software. The quarterly update deadlines for each tax year are:
— 5 August (covering 6 April to 5 July)
— 5 November (covering 6 July to 5 October)
— 5 February (covering 6 October to 5 January)
— 5 June (covering 6 January to 5 April)
You will still submit an End of Period Statement and a Final Declaration annually, which replaces the traditional Self Assessment return.
Using HMRC-compatible software
You cannot submit MTD quarterly updates through HMRC’s own website. You must use software that is recognised and approved for MTD for ITSA. Options that are well-suited to property landlords include FreeAgent, Hammock, and Xero — each of which allows you to record income and expenses, categorise transactions, and submit directly to HMRC.
Choosing the right software for your portfolio size and structure is worth doing carefully. Martin & Co Cardiff can point you in the right direction as part of our wider landlord support service.
The soft landing period — and when it ends
HMRC has confirmed a soft landing arrangement for the 2026/27 tax year (the first year MTD applies to the £50,000+ group). During this period, landlords who are already in scope will not face late submission penalties for quarterly updates if they miss a deadline — though late payment penalties still apply in full.
This grace period does not mean compliance can be ignored. From the 2027/28 tax year onwards, the points-based penalty system activates in full. Under this system, each missed quarterly submission earns a penalty point. Once you accumulate four points, a £200 financial penalty is triggered — and further penalties follow for continued non-compliance.
For Cardiff landlords entering scope in April 2027, there will be no extended grace period equivalent to the one currently in place. The expectation is that you will be ready from day one.
Jointly-owned properties — a common Cardiff arrangement
Many Cardiff couples and co-investors have purchased buy-to-let properties together, particularly in neighbourhoods like Canton, Pontcanna, and Roath where property values have risen steadily over the past decade. If you jointly own a rental property, it is important to understand how MTD applies.
Each owner is assessed individually on their share of the gross rental income. So if a property generates £36,000 per year and is owned equally between two people, each person’s share is £18,000 — below the £30,000 threshold on its own. However, if either owner has additional rental income from other properties, their combined gross figure may still bring them into scope.
Jointly-owned property arrangements can be complex, and the rules around how income is split for tax purposes (including declarations of beneficial interest) should be reviewed with a qualified tax adviser. Martin & Co Cardiff works alongside trusted professional partners to help landlords navigate these situations with confidence.
Welsh legislation and your responsibilities as a Cardiff landlord
As a landlord operating in Wales, your obligations are governed by the Renting Homes (Wales) Act 2016, which sets out the legal framework for occupation contracts with your contract holders. Compliance with Welsh housing legislation — including written occupation contracts, fitness for human habitation standards, and proper notice procedures — sits alongside your tax compliance responsibilities.
At Martin & Co Cardiff, we manage both dimensions on your behalf. Our team has over 30 years of experience in residential lettings and stays fully up to date with both Welsh legislation and evolving HMRC requirements, so you do not have to carry that burden alone.
Steps Cardiff landlords should take right now
The April 2027 deadline may feel distant, but the preparation required is not trivial. Here is what we recommend:
Calculate your current gross rental income across all properties, before any deductions, to establish whether you are likely to be in scope.
If you are close to or above £30,000, begin researching HMRC-compatible software options such as FreeAgent, Hammock, or Xero, and consider trialling one now so you are comfortable with it before the deadline.
Review any jointly-owned properties and seek advice on how income is attributed between owners for MTD purposes.
Speak to a qualified accountant or tax adviser who has experience with MTD for property landlords — ideally before the end of 2026.
Contact the team at Martin & Co Cardiff to discuss how our managed letting services can support your compliance journey, from record-keeping to regulatory updates.
Let Martin & Co Cardiff take the complexity off your hands
Managing a rental portfolio in Cardiff involves far more than finding good contract holders and collecting rent. Between Welsh housing legislation, HMRC compliance, maintenance responsibilities, and now Making Tax Digital, the administrative demands on landlords continue to grow.
Martin & Co Cardiff is here to simplify that journey. As part of a national network that manages more than 41,000 properties and lets 370 new properties every week, we bring the depth of a major network with the personal service of a dedicated local team who know the Cardiff market inside out — from the student lets of Cathays to the family homes of Heath and the period conversions of Roath.
Whether you manage one property or a substantial portfolio, our flexible service options — from Tenant Find through to our fully managed Premium Managed service — are designed to give you the level of support that suits your needs, with transparent fees and no hidden costs.
If you would like to understand what your rental income looks like and whether you are on track for MTD compliance, get in touch with Martin & Co Cardiff today. Our team is ready to offer straightforward, expert guidance with no obligation.
Book a free valuation with Martin & Co Cardiff to get a clear picture of your property’s current rental value and how it fits within your MTD planning.
Contact Martin & Co Cardiff directly to speak with one of our lettings experts about how we can support your compliance and portfolio management ahead of April 2027.
