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RTB dispute over a rent increase: how it works, what to attach, what you can win

When a tenant can dispute a rent increase with the RTB, the 28-day window and the cases with no deadline, the €30 fee, what to put in the application, and the €20,000 cap on what is awarded.

Published 22 September 2026 · checked against the Residential Tenancies Act and RTB guidance on 22 September 2026 · 7 min read

A pale blue corner house and brick terrace on a quiet Dublin street

A rent review notice lands on the table and says the rent goes up in 90 days. Fair enough, once a year the landlord is allowed to ask. Whether the figure is lawful is a different question, and the only place to test it is the Residential Tenancies Board’s dispute service. Here is how that works in 2026, without the forms-speak.

Two kinds of complaint, two different clocks

The RTB treats a rent dispute in one of two ways, and the deadline depends on which one you bring.

The notice is invalid. Since 1 March 2026 a Notice of Rent Review must give at least 90 days (the RTB’s guide to rent review notices walks through the form), state the new rent and its start date, cite three comparable tenancies from the public Rent Register with their RT numbers, state the floor area and BER of your home, and show the 2% or inflation calculation (section 22(2A)). A copy must reach the RTB within 7 days of being served on you (section 22(2), from 14 September 2026). Miss any of these and the notice does not take effect. There is no time limit on saying so: an invalid notice stays invalid.

The notice is valid but the figure is wrong. The form is right, but the increase is above what section 19(4) allows, or the three comparables are not really similar homes, or the new rent is above market rent. For this you have until the new rent takes effect or 28 days from receiving the notice, whichever is later (section 22(3)). In practice: the 90-day period is your window.

A third route has no deadline at all. A sitting tenant may ask the RTB to find that the rent is above market rent (section 19(1)), whether or not a notice was ever served. That is the route for a rent that was too high from the first day.

Notice servedday 0Copy to RTBlandlord's deadline28 daysdispute window closes, unless laterNew rent startsearliest lawful date
Days counted from the day the Notice of Rent Review is served on you

What it costs and where to apply

One online application through the RTB’s dispute process covers everything. Mediation is free. Adjudication costs €30. An appeal to a tribunal is €85, or €30 if you came through mediation first (Section 109 Rules 2025). Threshold will look over your case for nothing before you file.

Mediation ends in an agreement or a failure. If you agree, either party has 10 working days to withdraw (section 95(5A), from 14 September 2026); after that the agreement becomes a determination order with the same force as a decision. If it fails, the case goes to an adjudicator.

What to attach

An adjudicator decides on paper first and on the hearing second. Give them the paper.

  1. The Notice of Rent Review itself, every page, and the envelope or email it came in. The date of service matters for every deadline above.
  2. Your tenancy agreement and proof of the rent as it stands: bank statements or receipts for the last few months.
  3. The date the rent was last set. For a tenancy that never had a review, that is the day it began.
  4. The calculation. The RTB’s own rent calculator gives the maximum for your dates; our calculator uses the same CSO index and shows the two numbers side by side. If the notice asks for more, print both.
  5. The three comparables, checked. Look each RT number up in the Rent Register. Note floor area, bedrooms, BER and whether it was a new letting. If one of the three is a 110 m² house and you rent a 62 m² flat, say so, with the register entry beside it.
  6. What similar homes actually let for in your area in the same quarter, from the register, if you are arguing the market rent point.
  7. Any correspondence with the landlord about the increase, and any Notice of Exemption you received.

Keep the tone flat. Adjudicators read hundreds of these; the ones that win are lists of dates and figures with the source beside each.

What you can win, and the ceiling

The adjudicator can declare the notice invalid, set the rent at the lawful figure, and order the landlord to refund what you overpaid. The refund counts as damages, and section 115(3) of the 2004 Act caps damages at €20,000 per case. The High Court confirmed that reading in O’Sheehan, where a tribunal had awarded €29,660 in overpaid rent; the award stood only because the landlords did not appeal. Treat €20,000 as the practical ceiling. At €300 a month of overpayment that covers five and a half years; at €1,600 a month it covers one. The larger the overcharge, the less sense it makes to wait.

From 14 September 2026 the RTB also has its own stick, separate from your dispute: a fixed payment notice of €200 for a rent set above the section 19(4) limit or for a review notice not served correctly, after two warning letters, and a criminal offence if it goes unpaid. Paying it does not close your case.

If the landlord reacts

Section 14 forbids penalising a tenant for going to the RTB, giving evidence, or saying they intend to. Penalising includes acts that look lawful on their face, judged by how soon after the complaint they come (section 14(3)). A notice of termination served in response to a dispute is invalid (what a valid one needs is in our notice of termination guide), and in O’Sheehan the adjudicator valued the attempt at €2,000 in compensation, although the €20,000 ceiling had already been used up by the overpaid rent. In the first six months of a tenancy, when a landlord can still end it without a reason, some tenants wait for month seven before filing the market-rent complaint, which has no deadline. Weigh that against the ceiling above.

Before you apply

A Rent Check Report puts the three RT numbers from the landlord’s notice against the register, recalculates the 2% or inflation limit from the RTB’s own index, and lists every similar home let in your area. It is the exhibit an adjudicator expects to see.

Check my rent increase

Questions

I signed the new rent. Can I still dispute it?

Yes. Section 18 says a tenancy agreement cannot set aside the rent rules, so a signature under an increase above the limit does not make the increase lawful. In O'Sheehan, the tenants had paid the higher rent for years; the tribunal still ordered the overpayment back.

Does the landlord find out who complained?

Yes, a dispute is between the two parties and the landlord receives the application. Section 14 forbids penalising a tenant for going to the RTB, and a notice of termination served in response to a complaint is invalid. Adjudication hearings have been public by default since 14 September 2026, though names in closed hearings may not be published.

What if the notice never reached the RTB?

Ask the RTB. Since 14 September 2026 the landlord has 7 days from serving you to lodge a copy; without it the notice is not validly served under section 22(2), and the increase cannot take effect. The RTB can also issue the landlord a €200 fixed payment notice after two warning letters.

Can I go to mediation instead?

Yes, mediation is free and is offered on the same application form. If you reach an agreement, either side has 10 working days to withdraw from it; after that it becomes a binding determination order. If mediation fails you go to adjudication, and the €30 fee applies.

How much can I get back?

Rent set back to the lawful figure, and the overpayment refunded as damages, capped at €20,000 per case under section 115(3). The High Court in O'Sheehan treated the refund as damages within that cap, so a tenant overpaying €500 a month should not wait more than three years or so before applying.

Section numbers refer to the Residential Tenancies Act 2004 as amended, including by the Residential Tenancies (Amendment) Act 2025 and the Housing and Residential Tenancies (Miscellaneous Provisions) Act 2026. This is general information, not legal advice; Threshold and the RTB advise tenants and landlords free of charge.