Your Right To Written Reasons: Rule 35 And When The Tribunal Must Explain Its Decision

You received a letter from the First-tier Tribunal—headed with your case reference number, stating whether your appeal was allowed or dismissed, and setting out your right to appeal. But it doesn't explain why the tribunal decided as it did. Or it gives only a brief summary—a few paragraphs where you expected a full judgment. If you want to understand the tribunal's reasoning, or if you might want to appeal, you need to act fast. The deadline to request full written reasons is now just 14 days.

That deadline changed on 2 March 2026. If you've checked GOV.UK, you may have seen 28 days. That guidance has not been updated. The statute says 14 days. This article explains why that matters, how the rules work, and exactly what to do.

You Might Have Less Time Than You Think

On 2 March 2026, the Tribunal Procedure and Employment Tribunal Procedure (Amendment) Rules 2026 (SI 2026/115) came into force. Among other changes, it halved the deadline for requesting full written reasons from 28 days to 14 days.

As of March 2026, three official sources still say 28 days:

• GOV.UK's tax tribunal decision page
• GOV.UK's T242 guidance on appealing
• HMRC's internal guidance at ARTG8910

None had been updated at the time of writing. If you relied on 28 days and applied on day 21, your application would be late.

The statutory deadline is the one that counts. Rule 35(5) of the Tribunal Procedure (First-tier Tribunal) (Tax Chamber) Rules 2009 now says 14 days. That is the law.

What Rule 35 Actually Says

Rule 35 governs how the tribunal communicates its decisions. It creates three possible formats for a decision notice.

Full written reasons. The decision notice is accompanied by "full written findings of fact and reasons for the decision" (Rule 35(3)(b)). This is the full judgment—the kind published on BAILII. It sets out the facts the tribunal found, the law it applied, and why it reached its conclusion.

Summary reasons. The decision notice includes "a summary of the findings of fact and reasons for the decision" (Rule 35(3)(a)). A condensed version—enough to understand the outcome, but not the full reasoning.

Short decision (no written reasons). The decision notice states only the outcome and your appeal rights. No reasoning at all. Before the 2026 amendment, this required consent from all parties. Now, under new Rule 35(3A), the tribunal can issue a short decision without consent—provided it gave oral reasons at the hearing.

The critical rule is Rule 35(4): if the decision notice contains no reasons or only summary reasons, you can apply for full written reasons. And you must do so before applying for permission to appeal.

When You Need To Request Written Reasons

Whether you need to act depends on how your case was decided.

Default Paper Cases

If your case was decided on the papers—without a hearing—the tribunal must include at least summary reasons with the decision notice. There is no hearing, so there are no oral reasons, and the new Rule 35(3A) exception cannot apply. In practice, most Default Paper decisions include full reasons. But if you receive only a summary, you have 14 days to request the full version.

Oral Hearing, Decision Reserved

If the tribunal heard your case but reserved its decision—taking the case away to decide later—the written decision notice must include summary or full reasons (Rule 35(3)). Again, Rule 35(3A) does not apply because the reasons were not given orally at the hearing.

Oral Hearing, Decision Given At The Hearing

This is the new trap. If the tribunal announced its decision and gave oral reasons at the end of the hearing, the new Rule 35(3A) means the subsequent written decision notice need not include written reasons at all. You may receive a notice that simply says "your appeal is dismissed" (or allowed), with your appeal rights, and nothing more.

If you want written reasons—and you almost certainly should—you must apply under Rule 35(4) within 14 days of the tribunal sending the decision notice.

Practical tip: If you are attending a hearing, take careful notes of any oral reasons the tribunal gives. And consider asking at the hearing itself for full written reasons to be provided—or send your written request the same day. Do not wait for the decision notice to arrive by post and then start the 14-day clock under pressure.

Costs Decisions

Rule 35 applies to costs decisions. Rule 10 (the costs power) is in Part 2 of the rules, not Part 4. Rule 35(2) covers any decision "other than a decision under Part 4" that finally disposes of an issue. A costs decision that resolves the costs question is covered. You can request full written reasons for a costs decision, and the same 14-day deadline applies. If you are considering appealing a costs order, or if you want a public record of how the tribunal assessed unreasonable conduct, request the full written reasons. Our guide to unreasonable conduct costs covers the substantive framework.

Why Written Reasons Are Essential

Written reasons are not a formality. They serve three purposes that matter directly to you.

They Are A Mandatory Prerequisite For Appeal

Rule 35(4) says you "must" apply for full written reasons "before making an application for permission to appeal under rule 39." This is not optional. Without full written reasons, you cannot apply for permission to appeal to the Upper Tribunal.

If you skip the reasons request and go straight to a permission application, the FTT will typically treat your application as a request for reasons, give you the full decision, and let you decide whether to proceed. But relying on the tribunal to rescue you from a procedural error is not a strategy.

You Cannot Identify Errors Of Law Without Them

Appeals to the Upper Tribunal lie on "any point of law arising from a decision" (section 11, Tribunals, Courts and Enforcement Act 2007). The GOV.UK T399 guidance identifies four categories of legal error:

1. The tribunal didn't apply the correct law
2. There was a procedural error
3. There was no evidence to support a finding
4. The tribunal didn't give good enough reasons

Every one of these requires you to see the tribunal's reasoning. You cannot argue the tribunal applied the wrong law if you don't know what law it applied. You cannot argue there was no evidence for a finding if you don't know what findings it made. And the fourth category—inadequate reasons—is itself a ground of appeal, but only if you have the reasons to assess.

Requesting Does Not Shorten Your Appeal Window

The 56-day deadline for permission to appeal runs from the date the Tribunal sends you full written reasons (Rule 39(2)). Requesting reasons starts a separate, later clock—it does not eat into your appeal time. You lose nothing by requesting and gain the information you need to make an informed decision.

There is no fee and no form. The only cost is the time it takes to write a short letter or email.

What Counts As Adequate Reasons

Once you have the full written reasons, you may find they are thin—conclusory statements without real analysis, or reasoning that doesn't address the key issues in your case. If so, inadequate reasons can themselves be a ground of appeal.

The leading test comes from South Bucks District Council v Porter (No 2) [2004] UKHL 33, where Lord Brown set out the standard at paragraph [36]:

"The reasons for a decision must be intelligible and they must be adequate. They must enable the reader to understand why the matter was decided as it was and what conclusions were reached on the 'principal important controversial issues', disclosing how any issue of law or fact was resolved."

The Court of Appeal put it more bluntly in English v Emery Reimbold & Strick [2002] EWCA Civ 605, at paragraph [16]:

"justice will not be done if it is not apparent to the parties why one has won and the other has lost"

The reasons don't need to address every argument. But they must cover the principal controversial issues—the points that actually mattered. If the tribunal decided against you on a key factual dispute and said nothing about why it preferred HMRC's evidence over yours, that may be an inadequate-reasons error.

If the Upper Tribunal finds the FTT's decision involved an error of law—including inadequate reasons—it can set the decision aside and either remit it to the FTT for a fresh hearing or remake it (section 12, TCEA 2007). In practice, inadequate-reasons cases are usually remitted for rehearing, sometimes before a different panel.

For guidance on identifying errors of law and drafting your grounds, see our guide to writing grounds of appeal.

How To Request Full Written Reasons

There is no form. The Tribunal Procedure Committee's consultation response described the process as "simple and not requiring of legal advice or assistance" (paragraph 77). Here is what to do.

Step 1: Write A Short Letter Or Email

Address it to:

First-tier Tribunal (Tax Chamber)
PO Box 16972
Birmingham B16 6TZ

Email: [email protected]

Include:

• Your case reference number (on your decision notice)
• The date of the decision you are applying about
• A clear statement that you are applying under Rule 35(4) for full written findings of fact and reasons

A request along these lines is sufficient:

Dear Sir/Madam,

Case reference: TC/2026/00000

I received the tribunal's decision notice dated [date] in the above case. The decision notice [contains summary reasons only / does not contain written reasons].

I apply under Rule 35(4) of the Tribunal Procedure (First-tier Tribunal) (Tax Chamber) Rules 2009 for full written findings of fact and reasons for the decision.

Yours faithfully,
[Your name]

Step 2: Meet The 14-Day Deadline

Your application must be received by the tribunal within 14 days of the date the tribunal sent the decision notice (Rule 35(5)). Not 14 days from when you received it—14 days from when it was sent. If the decision notice is dated 1 April, the deadline is 15 April.

If you are posting, allow time for delivery. Email is safer if the deadline is tight.

Step 3: Copy HMRC

The rules don't require you to copy HMRC, but it is good practice. The tribunal will serve the full written reasons on all parties when they are produced (Rule 35(6)), but sending a copy keeps things transparent.

Step 4: Wait For The Full Reasons

The tribunal must provide full written reasons "as soon as reasonably practicable" after receiving your application (Rule 35(6)). There is no fixed deadline for the tribunal's response.

If You Miss The 14-Day Deadline

The tribunal has a general power to extend time under Rule 5(3)(a). If you miss the deadline, you can apply for an extension—but you will need to explain why you were late, and the tribunal is not obliged to grant it. Do not rely on this. Request reasons as soon as you receive a decision notice that does not include full written reasons.

What Changed On 2 March 2026

The 14-day deadline is the most practically significant change, but SI 2026/115 made four amendments to Rule 35.

1. Decision notice timing (Rule 35(2)). The old rule required the tribunal to send the decision notice "within 28 days" of the decision. The new rule says "as soon as reasonably practicable." The Tribunal Procedure Committee explained that the 28-day period was unrealistic for complex cases and unnecessary for simple ones.

2. Consent removed (Rule 35(3)). Previously, the tribunal had to include reasons in the decision notice "unless each party agrees that it is unnecessary." That consent provision has been deleted. But its removal is balanced by the new oral reasons exception.

3. Oral reasons exception (Rule 35(3A)). Where the tribunal gave oral reasons at a hearing—whether summary or full—the written decision notice need not include written reasons. This is new and untested. It means that after an oral hearing where the tribunal announces its decision and explains its reasoning verbally, the subsequent written notice may arrive bare.

4. Request deadline halved (Rule 35(5)). From 28 days to 14 days.

One significant proposal was dropped. The original consultation proposed restricting the right to request written reasons to the unsuccessful party only, with a discretionary gateway for successful parties. This was abandoned after opposition. The Tribunal Procedure Committee concluded: "as a matter of principle both parties (successful or unsuccessful, and however defined) should be entitled to request written reasons" (consultation response, paragraph 113). Either party can still request.

Key Deadlines At A Glance

The 14-day and 56-day deadlines are sequential, not overlapping. Request your reasons, receive them, and then you have 56 days from the full reasons to apply for permission to appeal. Requesting reasons preserves your appeal window—it does not consume it.

For the full post-decision timeline, see our guide to what happens after your tribunal decision.

This article is for informational purposes only and does not constitute legal or tax advice. For advice specific to your situation, consult a qualified tax adviser, accountant, or solicitor.