Turning AEAT Billing Choices Into Your First Line of Defence
If you are a UK resident with Spanish links and the AEAT has written to you, your first instinct is usually to think about the tax risk. But the fee agreement you sign with your Anglo-Spanish Lawyer or Barrister can quietly become your first line of defence as well. It will decide how deeply your case can be worked, how much control you have over costs, and how much risk you carry if the investigation grows.
In our cross-border work, we see that the right billing structure often makes the difference between a calm, steady defence and a stressful scramble. Here we focus on Spanish tax investigation defence and explain what you should ask about fixed fees, hourly billing, scope, caps, success fees, and disbursements before you agree to representation.
Why AEAT Investigations Are Not Routine Tax Work
An AEAT investigation is very different from asking a professional to help with a tax return. It can cover several years at once, raise questions about where you are really tax resident, and test how double tax treaties apply to your income and assets. On top of back taxes, there can be surcharges, interest, and sometimes the risk of criminal or reputational issues.
UK residents with Spanish assets or residency links are under closer AEAT attention because of:
- CRS data sharing between countries
- Spanish property registry information
- Data flows between HMRC and AEAT
- Triggers such as non-resident property ownership or undeclared foreign assets
This cross-border focus means your Lawyer or Barrister needs time to collect facts, align UK and Spanish positions, and build technical arguments. If the fee model does not support careful work and sustained negotiation, you might feel pushed to accept outcomes that are not in your best interest simply because you fear open-ended costs.
Fixed-Fee Arrangements That Truly Protect You
Fixed fees can be a relief when you are dealing with an AEAT letter on your kitchen table. They can give clarity at a worrying time, as you know in advance what you will pay for a well-defined part of the defence.
For Spanish tax investigation defence, a fixed-fee agreement might cover:
- An initial risk review and advice on your exposure
- Preparing written submissions in response to AEAT requests
- Meetings or calls with the tax inspector
- Advice on settlement options or moving into appeal
The best way to make fixed fees work for you is to break the matter into phases, for example:
- Early case assessment and strategy
- Responding to initial information requests and proposals
- Negotiation or settlement discussions
- Administrative appeals or court stages, if needed
You should always ask for the scope of each phase in writing. Ask what is included and what is clearly not included. For example, does the fixed fee cover drafting appeal documents, attending hearings, reviewing new AEAT data, or only the first written response?
Fixed fees have clear strengths: easier budgeting, less stress about each email or call, and the chance to plan in sterling even if some work is billed in euros. The risk is under-scoping. AEAT may decide to add new tax years or new issues, which can move the case far beyond the original plan.
A helpful question to put to your Lawyer or Barrister is: how often will we revisit the fixed fee if AEAT widens the investigation? You want to know when a new scope will be discussed and how that will be agreed.
When Hourly Billing Makes Sense and How to Control It
Hourly billing can sound risky if you are already under pressure from AEAT. However, there are situations where it is more realistic than a fixed fee, for example:
- The issues are novel or unclear at the start
- AEAT is sending frequent, changing requests
- There is a tight timetable and fast reaction is needed
In an hourly model, it is important to talk about caps and estimates. A soft cap is an agreed figure where the firm tells you as they approach it, then you both decide how to proceed. A hard cap is an upper limit where fees will not go beyond a set amount without express agreement.
When discussing hourly billing, you should ask for:
- Written hourly rates for all team members, including any Barrister
- A clear explanation of any different rates for work in Spain and the UK
- Monthly time reports that show what has been done and by whom
You can also agree some practical controls, such as:
- Prior approval if extra work is expected to exceed a certain number of hours
- Simple communication rules, for example when to use email or calls
- Early warnings if the original estimate no longer matches AEAT activity
This keeps you involved in decisions about the depth of work on your defence and lets you decide how much risk you are comfortable carrying at each stage.
Success Fees, Disbursements and Currency Risks
In some Spanish tax investigation defence matters, firms may suggest a blended structure, for example a base fixed or hourly element plus a success fee. The success part might be tied to:
- Reductions in assessed tax
- Cancellation or reduction of penalties
- Achieving a particular settlement outcome
The idea is to align interests, but success fees can be complex in cross-border tax, so you should ask exactly what result counts as success, how it is measured, and when it becomes payable.
Disbursements are another key point. These are third-party costs that sit on top of legal fees, such as:
- AEAT or court filing fees
- Translation and sworn interpreter costs
- Expert reports or valuations
- Notary and document authentication expenses
- Courier or official copy charges
You should ask which disbursements are likely in your case, who will incur them, and in which country. Clarify whether they will be billed as they arise or grouped into regular statements.
Finally, there is the currency angle for UK residents with Spanish exposure. Some fees or disbursements may naturally be in euros, others in pounds. Exchange rate moves between the UK and Spanish tax year-ends can affect what you actually pay. It is worth asking:
- In which currency each part of the work will be billed
- Whether currency conversions are done at bank rates or other reference points
- If you can reduce uncertainty through agreed payment schedules or minimum and maximum ranges
Questions to Ask Before You Sign Any Fee Agreement
Before you sign anything, it helps to have a short checklist in front of you. Useful questions include:
- What is the exact scope of work you are proposing for this investigation?
- Which phases of the AEAT process are covered and which are not?
- How will we agree any extra work if AEAT opens new years or issues?
- What are your hourly rates, and how and when might they change?
- Are fixed fees, caps, or blended models available for parts of the case?
You should also ask about experience. Spanish tax investigation defence for UK residents is a niche area. Helpful questions might be:
- How often do you act for UK residents under AEAT investigation?
- Are you comfortable with both UK and Spanish tax rules and how they interact?
- How familiar are you with AEAT settlement practices and appeal routes?
Request a written, plain-language engagement letter that makes sense in both UK and Spanish professional environments. Taking time to compare at least two proposals can help you balance cost predictability, depth of technical work, and cross-border experience. At Del Canto Chambers, as an Anglo-Spanish chambers, we see how important that balance is for clients split between the UK and Spain.
Secure Your Position with the Right Fee Strategy
Waiting for the next AEAT communication before thinking about fees can leave you cornered. Early planning, even before an investigation starts, lets you think calmly about how you would fund a defence and what fee structure best suits your risk profile. This can also give you more space to discuss scope, caps, and billing models on terms that suit you.
If you already have an AEAT letter, the most helpful step is often to gather your documents and seek integrated Anglo-Spanish advice quickly. That way, fee discussions happen alongside early risk assessment, not in the middle of a deadline crisis. With the right cross-border team and a fee structure that matches the complexity of your case, you give yourself the best chance of handling Spanish tax investigation defence with control and confidence.
Protect Your Wealth With Specialist Spanish Tax Investigation Support
If you are facing questions from the Spanish tax authorities, we can provide clear, strategic guidance to protect your position. Our dedicated Spanish tax investigation defence service at Del Canto Chambers is designed to minimise risk and resolve disputes efficiently. Speak to our team today via our contact page so we can review your situation and start building a robust response.
