Making Tax Digital for Income Tax Self Assessment (MTD ITSA) arrives in April 2026. If your agency generates more than £50,000 in self-employed or partnership income, you will be required to file quarterly updates through MTD-compatible software rather than a single annual return.

This is not a minor tweak to the filing process. It is a fundamental change in how you report income and expenses to HMRC. For agency founders running limited companies, the impact is indirect but still real. For sole traders and partnerships, it is immediate and mandatory.

Here is what MTD ITSA means for your agency, when it applies to you, and what you need to do before the first deadline.

What Is MTD ITSA?

MTD ITSA stands for Making Tax Digital for Income Tax Self Assessment. It is the second phase of HMRC’s long-term plan to digitise the tax system. The first phase, MTD for VAT, has been mandatory since 2019. MTD ITSA applies the same principle to income tax.

Instead of filing one self assessment return after the tax year ends, you will submit four quarterly updates to HMRC during the year. Each update summarises your income and expenses for that quarter. After the year ends, you submit a final declaration to confirm the figures and make any adjustments.

HMRC’s stated aim is to reduce the £8 billion annual tax gap caused by errors and late filing. Their data shows that digital record-keeping reduces mistakes. Whether you agree with the policy or not, it is happening.

When Does MTD ITSA Apply to Agency Founders?

The rollout is phased by income level:

  • April 2026: Mandatory for sole traders and partnerships with total self-employed or partnership income above £50,000 per year.
  • April 2027: Extended to those with income above £30,000 per year.
  • Beyond 2027: HMRC has not yet confirmed a date for those below £30,000, but it is expected within the next five years.

Income here means gross income from self-employment or partnership, not profit. If your agency turns over £60,000 but your profit after expenses is £25,000, you still fall into the first wave.

For agency founders who operate through a limited company, you are not directly caught by MTD ITSA unless you also have self-employed income outside the company. However, your company is already subject to MTD for VAT if your turnover exceeds £90,000. And if you are a director drawing salary and dividends, your personal tax position is not affected by MTD ITSA at this stage. Corporation Tax MTD is coming, but that is a separate change expected around 2027.

What Changes for Agency Founders Under MTD ITSA?

Four specific changes matter to you.

1. Quarterly Filing Instead of Annual

Currently, you file one self assessment return by 31 January each year. Under MTD ITSA, you will file four quarterly updates plus a final declaration. The quarterly deadlines are:

  • Period 1 (6 April to 5 July): file by 5 August
  • Period 2 (6 July to 5 October): file by 5 November
  • Period 3 (6 October to 5 January): file by 5 February
  • Period 4 (6 January to 5 April): file by 5 May

The final declaration replaces the current self assessment return. It is due by 31 January following the end of the tax year, exactly as now.

2. Digital Record-Keeping Is Mandatory

You must maintain digital records of all income and expenses. Spreadsheets are acceptable only if they integrate with MTD-compatible software through a bridging tool. Manual records on paper or in a basic spreadsheet without bridging software will not comply.

This means your agency needs accounting software that is MTD ITSA compliant. Our ICAEW-qualified team works with Xero, QuickBooks, FreeAgent, and Sage, all of which are MTD-ready. If you are using a spreadsheet-only system, you need to upgrade before April 2026.

3. Quarterly Figures Are Not Final

A common concern we hear from agency founders is: "What if my quarterly figures are wrong?"

The quarterly updates are cumulative estimates. They do not need to be perfect. You can adjust them in the final declaration. The key requirement is that you submit something reasonable within 30 days of each quarter end. HMRC expects you to use the best information available at the time.

If you realise in December that your July estimate was wrong, you correct it in the final declaration. There are no penalties for adjusting quarterly figures, provided you are not deliberately misreporting.

4. No More Paper Returns

If you currently file a paper self assessment return, that option disappears once MTD ITSA applies to you. Everything must be filed digitally through MTD-compatible software.

What MTD ITSA Means for Different Agency Structures

The impact varies depending on how your agency is set up.

Sole Trader Agency Founders

This is the group most directly affected. If you run your agency as a sole trader and your gross income exceeds £50,000, you must comply from April 2026. If your income is between £30,000 and £50,000, you have until April 2027.

For a sole trader web designer turning over £65,000 per year, MTD ITSA means quarterly bookkeeping becomes mandatory. You cannot leave it until January. You need a system that captures income and expenses in real time.

Partnerships

Partnerships are treated similarly to sole traders. Each partner’s share of partnership income counts toward their individual threshold. If you are in a two-person agency partnership and each partner’s share is £40,000, you both fall into the 2027 wave.

The partnership itself must file quarterly updates for the partnership’s income and expenses. Each partner then reports their share on their personal final declaration.

Limited Company Agency Founders

If your agency is a limited company, MTD ITSA does not apply to your director’s salary or dividends. You are not required to file quarterly updates for your personal tax affairs.

However, if you have side income from self-employment (consulting, freelance work, speaking fees) that exceeds the threshold, that income is subject to MTD ITSA. Many agency founders have side projects. If you do, check your total self-employed income across all sources.

Your company itself is already subject to MTD for VAT if it is VAT-registered. If you are not VAT-registered but your turnover exceeds £90,000, you must register and comply with MTD for VAT. That is a separate requirement.

Software and Record-Keeping Requirements

HMRC has published a list of MTD-compatible software products. The main options for agency founders are:

  • Xero, widely used by agencies, MTD ITSA compliant, integrates with Dext for receipt capture
  • QuickBooks, similar functionality, good for smaller agencies
  • FreeAgent, popular with sole traders and micro-agencies, includes built-in bank feeds
  • Sage, more traditional, still MTD-compliant
  • Spreadsheets with bridging software, possible but clunky. You need a bridging tool that connects your spreadsheet to HMRC’s API

If you currently use a spreadsheet and nothing else, you need to change. The bridging software route works but adds complexity. Most agency founders find it simpler to move to proper accounting software.

Receipt capture is also important. You need digital copies of all receipts and invoices. Digital agencies often already do this because they work online. For creative agencies that still deal in paper receipts, now is the time to digitise.

Penalties for Non-Compliance

HMRC has introduced a new points-based penalty system for MTD ITSA. It replaces the current late filing penalty structure.

You receive one penalty point for each missed quarterly deadline. Once you accumulate four points, you face a £200 penalty. Additional points after that trigger further penalties. Points expire after two years of compliance.

Late payment penalties remain separate. If you do not pay your tax on time, you incur interest and surcharges as before.

The system is designed to be more forgiving for occasional mistakes but stricter for persistent non-compliance. Missing one quarterly deadline because you were busy with a client project will not trigger a fine. Missing four in a row will.

How to Prepare for MTD ITSA Now

April 2026 sounds distant. It is not. Here is what to do between now and then.

1. Check Your Income Level

Look at your gross self-employed income for the 2024/25 tax year. If it exceeds £50,000, you are in the first wave. If it is between £30,000 and £50,000, you have an extra year. If it is below £30,000, you are not yet caught but will be eventually.

Do not forget to include partnership income and any self-employed side income.

2. Choose Your Software

If you are not already using MTD-compatible accounting software, select one and migrate your records. This is not a task for March 2026. Do it now while you have time to learn the system and iron out issues.

Most software providers offer free trials. Test two or three options before committing. Contact our team if you want recommendations based on your agency size and structure.

3. Set Up Digital Record-Keeping

Start keeping digital records now, even if MTD ITSA does not apply to you yet. It builds good habits. Use receipt capture apps like Dext or Hubdoc. Connect your business bank account to your accounting software so transactions flow in automatically.

If you run a marketing agency with multiple income streams, categorising transactions as they happen saves hours at year-end.

4. Review Your Cash Flow

Quarterly filing means quarterly tax payments. HMRC will calculate your estimated tax liability based on each quarterly update and expect payment on account. This changes cash flow timing.

Under the current system, you pay tax once a year (or twice if you make payments on account). Under MTD ITSA, you may be paying smaller amounts more frequently. For agencies with lumpy cash flow from project-based work, this requires planning.

Set aside a percentage of each invoice into a separate tax savings account. 20% for basic rate taxpayers, 40% for higher rate. It prevents surprises.

5. Talk to Your Accountant

If you work with an accountant, ask them about their MTD ITSA readiness. Agency Founder Finance are ICAEW qualified accountants and we are fully prepared for MTD ITSA. We help our clients set up software, categorise transactions, and file quarterly updates.

If you do not use an accountant, consider engaging one before the deadlines hit. The quarterly filing requirement adds administrative burden. An accountant reduces that burden and ensures compliance.

Common Myths About MTD ITSA

We hear several misconceptions regularly. Let me clear them up.

"MTD ITSA only applies to large businesses." No. It applies to any sole trader or partnership with income above the threshold, regardless of business size. A one-person agency turning over £55,000 is caught.

"I can just file my quarterly updates once a year." No. The quarterly updates are separate legal filings. You must submit each one within 30 days of the quarter end. HMRC can see whether you have filed on time.

"My accountant will handle everything." Partly true. Your accountant can file the quarterly updates on your behalf, but you still need to provide accurate digital records. If your receipts are in a shoebox, your accountant cannot file on time.

"MTD ITSA means I pay more tax." No. The tax you owe is calculated on your actual profit, exactly as now. MTD ITSA changes the filing process, not the tax calculation.

What About Corporation Tax MTD?

HMRC is also planning MTD for Corporation Tax. The current timeline suggests mandatory filing from around 2027, but this has not been confirmed. It will require limited companies to file quarterly updates on their corporation tax position.

For agency founders with limited companies, that is a future concern. For now, focus on MTD ITSA if you have self-employed income, and MTD for VAT if your company is VAT-registered.

Final Thoughts

MTD ITSA is coming. It changes how you report income and expenses to HMRC. For most agency founders, the main impact is administrative: you need better record-keeping habits and MTD-compatible software.

The tax you pay does not change. The deadlines do. And if you are prepared, the quarterly updates become a useful discipline rather than a burden. They give you a clearer picture of your agency’s financial health throughout the year, not just at year-end.

If your contractor mix has changed in the last 12 months, or if you have taken on self-employed side work alongside your agency, check your income level now. Then choose your software, set up digital records, and speak to your accountant before the end of 2025.

That gives you 18 months to prepare. Use them.