When You Need Three Comparables

The RTB Rent Register is the RTB's published record of the rents being paid on registered tenancies. Since 1 March 2026, it is also the reference point for one question every rent now has to answer: is this rent above market rent? The RTB's guidance is that you use information from the Register to show it isn't, by giving three examples of the most recent rents paid for similar properties in a comparable area.

The legal test behind "similar" is now spelled out: dwellings of a similar size (measured by floor area), number of bedrooms, type and character, and — where it applies — BER, in a comparable area. Hold on to that list. Every step below is about satisfying it, and only some of it is something the Register can filter for you.

Where it bites depends on what you are doing with the rent:

Situation What caps the rent What the comparables do
New tenancy, rent reset to market
Dwelling not let for 2 years, or a Part D exemption — e.g. the last tenant left voluntarily		 Market rent only They are the ceiling. The whole case for the figure rests on them.
New tenancy, previous rent carries over
e.g. the last tenancy ended on a no-fault ground		 The national rent cap from the last rent and the date it was set Part C of the Notice of Rent Setting still asks for three — they show the capped figure isn't above market either.
Rent review, sitting tenant The cap: the lower of 2% a year or CPI, once in 12 months, 90 days' notice The RTB frames the test around market rent — check its rent review guidance for your facts. Including them costs nothing; omitting them where required can cost the notice.
Same tenant, new fixed term The cap — a renewal is a continuation, not a reset As for a review. There is no "reset on renewal".

This page is the how. If you need the whether — which endings allow a reset to market rent and which carry the old rent forward — start with how to set rent under the 2026 rules, then come back.

Two Ceilings: The Cap and the Market

The most common misunderstanding about the Register is that it tells you what you're allowed to charge. It doesn't. It tells you what the market is paying. The legal maximum is the lower of two separate numbers:

Ceiling 1 · The national rent cap Last rent × the lower of 2% a year or CPI, to the new start date — where a cap applies. Your rent increase calculator figure.
Ceiling 2 · Market rent What three genuinely comparable tenancies on the Register are paying. Your Part C figure.
Lawful rent ≤ whichever is lower
Comparables never lift a capped rent. On a reset, they are the only limit.

So comparables can lower what you can charge, but they can never raise a capped rent. A three-bed whose rent has been carried over at €1,700 doesn't get to €2,100 because the street is now paying €2,100 — the cap governs until a lawful reset point. Our national rent cap field guide covers Ceiling 1. The rest of this page is Ceiling 2.

What to Have in Hand Before You Search

The search takes minutes. The mistakes happen before it, when someone types a floor area from memory or guesses the BER. Assemble the subject property's facts first, from documents you'd be happy to show an adjudicator:

  • Eircode — this is what the Register uses to find the Local Electoral Area.
  • Dwelling type — apartment, house and so on, as you'd describe it on the registration.
  • Number of bedrooms — the Register requires an exact match on this.
  • Floor area in m² — one measured figure, with its source noted. Gross from one document and net from another is how a 10% band quietly goes wrong.
  • BER rating — from the current certificate, not last year's advert.
  • The character notes the Register can't filter — own-door or apartment block, floor level, period or new build, outdoor space, parking, condition, furnished or not.
  • The rent you intend to set, and — if a cap applies — the last rent and the date it was set.

Use the same numbers everywhere

Floor area and BER appear on the RTB registration, on the Notice of Rent Setting and in the Register search. If the three disagree, the first question at a hearing will be which one is true. Capture them once, from the source document, and reuse them.

The RTB Rent Register, Screen by Screen

The Register lives on rtb.ie and is free to use without logging in. TenantSync isn't affiliated with the RTB; the steps below describe how the RTB says the search behaves, and the layout on the day may differ from our description.

  1. Set the area

    Enter the property's Eircode or address. The Register matches it to a Local Electoral Area and returns results only from that area. It does not rank by distance from your property. Where your own area has no good matches, you can search a comparable area by choosing a different one — note why you did.

  2. Describe the dwelling

    Enter the dwelling type, number of bedrooms, floor area and BER — the facts you assembled above.

  3. Read the ranking, not just the rents

    The Register returns a short ranked list — the RTB describes up to 10 results. Exact matches come first: same bedrooms, same BER and floor area within 10% of yours. If there are fewer than 10, weaker matches fill the list: first those that differ only on BER, then those whose floor area is more than 10% away. Note which kind each result is.

  4. Choose three — on character as well as attributes

    Shortlist the exact matches, then test each one against the things the Register can't see: type and character, floor level, outdoor space, condition. Prefer the most recent rents. You do not have to use the first three results — and often you shouldn't (see why).

  5. Record each one

    For each comparable, write down its RT number (the registered tenancy number) and its rent — these are what the notice cites. Add your own note of why you chose it and how it differs from the subject property.

  6. Save the results, with the date

    Download or print the results page. The Register is live data: new tenancies register, rankings move, and the list you saw today will not be the list a tenant sees in six months. A dated printout is the only way to show what the Register said when you set the rent.

  7. Test the rent against both ceilings

    Is your figure at or below what the three comparables support? If a cap applies, is it also within the cap? If it's above the comparables, stop and ask whether you can genuinely justify it as market rent — because the Register says otherwise.

  8. Complete the notice and file the pack

    Enter the three RT numbers and rents in Part C of the RTB's prescribed notice, serve it, copy it to the RTB within the deadline, and file the printout, your notes and the notice together against the tenancy.

What a results list can look like

Here is an invented example for a two-bed apartment, 68 m², BER B2, where the landlord is entitled to reset to market and the agent proposes €1,950 a month.

Subject 2 bed apartment · 68 m² · BER B2 · proposed €1,950
# Floor area BER Rent Match & verdict
1 · 2 bed apt 72 m² (+6%) B2 €2,150 Exact Skip Top-floor unit with a large terrace — not similar in character.
2 · 2 bed apt 66 m² (−3%) B2 €1,925 Exact Use Same block type, mid floor, balcony.
3 · 2 bed apt 70 m² (+3%) B2 €1,980 Exact Use Similar age and spec.
4 · 2 bed apt 64 m² (−6%) B2 €1,900 Exact Use Smaller, otherwise alike.
5 · 2 bed apt 69 m² (+1%) B3 €1,940 Weaker · BER Reserve if one of 2–4 falls away.
6 · 2 bed apt 81 m² (+19%) B2 €2,200 Weaker · size Skip Outside the 10% band.
Invented figures for illustration — not the RTB's interface and not real Register data. RT numbers omitted.

Result 1 ranks first and carries the highest rent. It is also the one an adjudicator would pick apart: a penthouse with a terrace isn't "similar in character" to a mid-floor flat. Results 2, 3 and 4 support €1,900–€1,980, and €1,950 sits comfortably inside that range. Had the agent taken the top three by rent instead (1, 6 and 3), the "evidence" would have pointed to over €2,100 — and fallen apart the first time a tenant looked at it.

Why the First Three Results Are Usually the Wrong Three

The Register ranks by how well a tenancy matches the attributes you typed in. That's useful, and it's not the same thing as "comparable". Five reasons the top of the list is a starting point, not an answer:

It can't see character

Type, character and condition are part of the test, but only type is a search field. A period conversion and a 2019 block can be an exact match on paper.

An LEA is not a neighbourhood

Results come from the whole Local Electoral Area, not the nearest streets. Two exact matches can sit in markets that rent very differently.

Weaker matches fill thin areas

With fewer than 10 exact matches, BER-mismatched and size-mismatched tenancies appear in the same list. Easy to cite one without noticing.

Recency matters

The RTB asks for the most recent rents. An older tenancy in a fast-moving market understates — or overstates — what the market pays now.

Highest-first looks like cherry-picking

Three comparables that happen to be the three highest rents in the list is the pattern a tenant's representative will look for first.

The defensible habit is simple: shortlist the exact matches, rule out the ones that fail on character, choose the most recent of what's left, and write one line on each saying why. That line is what turns three numbers into an argument.

Free Comparables Match Checker

Before you commit three comparables to a notice, check them against the subject property the way the Register grades a match — and see whether your proposed rent sits inside the range they support. It's pre-filled with the example above; change anything.

Comparables match checker

Grades each comparable against the RTB's described match rules (same bedrooms, same BER, floor area within 10%) plus type and area, and compares your rent to the range. Runs entirely in your browser — nothing is sent anywhere.

Your property
Comparable 1

—

Comparable 2

—

Comparable 3

—

Exact matches —
Range the comparables support —
Your rent against that range —

—

    A sense-check, not a ruling. The grading follows the RTB's published description of how the Register matches (same bedrooms, same BER, floor area within 10%) and adds type and area, which the Register filters on. It can't judge character — floor level, outdoor space, condition, period or new build — which is part of the legal test and yours to assess. Where your rent sits outside the range, it doesn't mean the rent is unlawful; it means you need to be able to justify it. Confirm the rules on rtb.ie.

    Filling in the Notice: Part C and Friends

    On a new tenancy, the comparables travel on the RTB's prescribed Notice of Rent Setting. Part C is where they live, but it only makes sense alongside the parts around it — and the parts around it are where a careful Part C gets undone by a careless field elsewhere.

    Part What it holds Where agents slip
    A · The dwelling Address, Eircode, previous and current RT numbers, tenancy start date, floor area, BER, and whether it's a new apartment or SSA where development commenced from 10 June 2025 A floor area or BER that doesn't match the one used in the Register search
    B · The rent The new rent, the last rent and the date it was set, the rent control rule applied, and whether the RTB Rent Calculator output is attached Last rent or date missing, so the cap can't be checked
    C · Comparables Three comparable dwellings from the Register — each by RT number and rent Two comparables, or an address instead of an RT number
    D · Exemption Any ground claimed for setting the rent outside the cap — no tenancy in two years, substantial change, or how the last tenancy ended Claiming a ground with no evidence, or a substantial-change ground without the declaration
    E · Documents The supporting documents attached — e.g. BER certificates, an architect's letter, planning permission "Attached" ticked, nothing attached

    Part D is where a reset is claimed — so Part C has to carry it

    The grounds in Part D fall under three headings: no tenancy (none in the two years before this one; or none in 12 months for a protected structure), substantial change (a permanent extension adding at least 25% of floor area; a BER improved by seven or more ratings; or at least three of five listed works — each with a declaration that the works weren't done solely to meet minimum standards), and end of tenancy or cycle (the tenant ended the last tenancy; it ended for breach or because the dwelling no longer suited them; or, for student-specific accommodation, the end of a three-year cycle). Claim one and the cap falls away — leaving Part C as the only thing standing between your figure and a successful challenge.

    Serving It: The Tenant and the RTB

    Two recipients, two clocks — and the clocks differ by notice type, which is exactly why they get confused.

    Notice Tenant Copy to the RTB
    Notice of Rent Setting (new tenancy) At the start of the tenancy — by email, post or hand delivery Within one month of the tenancy start date, per the RTB's current guidance
    Notice of Rent Review (sitting tenant) At least 90 days before the new rent applies Within 7 days of the date the tenant was served (since 14 September 2026)

    Both go to the RTB through its online Service Centre — see our guide to the RTB portal. Our advice is the same for both: send the RTB copy the day you serve the tenant. One action, nothing pending, and no window in which a holiday or a sick day turns into a breach. The full review rules are in why your rent review notice can be invalid.

    Since 14 September, the slips are cheaper to fine

    The RTB can now issue fixed payment notices without opening an investigation, and three of the six breaches sit squarely on this page: failing to give rent setting information at the start of a tenancy, failing to notify the RTB of a rent exemption, and setting rent above the legal limit — €100 for the first two, €200 for a rent breach. The fine is the small part: any excess collected is repayable, and adjudication reports for disputes applied for from 14 September are published with the property address. See the hidden cost of poor tenancy compliance.

    The Evidence Pack to Keep

    An incoming tenant can refer the rent to the RTB if they believe it's above market rent. Under six-year Tenancies of Minimum Duration, the rent you set on day one is the base every later review is measured from — so the file behind it may be opened years from now, by someone who wasn't there. Build it as if that someone is an adjudicator, because they might be:

    1. The dated Register printout The results as they appeared on the day, with the search inputs visible.
    2. The three comparables, with your reasoning RT number, rent, and one line each on why it's comparable — and why higher-ranked results were set aside.
    3. The subject property's facts and their sources Floor area and BER as used, and the documents they came from.
    4. The cap calculation, if a cap applied Last rent, date set, the rule applied (2% or CPI) and the CPI figure — the RTB Rent Calculator printout.
    5. Part D evidence, if a reset was claimed Why the last tenancy ended, or the works and certificates behind a substantial-change ground.
    6. The notice exactly as served Not a regenerated copy — the PDF the tenant received.
    7. Proof of service on the tenant and the RTB How and when the tenant got it, and the RTB submission confirmation.

    Keep it against the tenancy, not in the inbox of whoever happened to do the let. Agencies don't lose disputes because their comparables were weak. They lose them because the comparables were in a negotiator's downloads folder and the negotiator left in March.

    Doing It 120 Times a Month

    For a landlord with four properties, the comparables step is an evening a year. For an agency it is a production line — and production lines fail differently. The issue isn't whether a skilled negotiator can pick three good comparables. It's whether every negotiator does, the same way, on a Friday in August, and whether the result can be found again.

    Worked example: one mid-sized agency's month

    An agency managing 300 tenancies does 15 new lets and 25 rent reviews in a month — 40 notices.

    • Comparables sourced: 40 × 3 = 120 a month, or 1,440 a year
    • At 25 minutes per notice to gather the facts, search, choose, record and file: 40 × 25 = ~17 hours a month
    • Evidence packs that must be retrievable on demand: 480 new ones a year, each tied to a tenancy that may run six years

    The search is the cheap part. The expensive parts are variance between negotiators and retrieval a year later — and neither shows up until a tenant disputes a rent. Illustrative figures; use your own.

    That's the case for a standard operating procedure: the same facts captured the same way, a written selection rule, a reviewer on resets, and one place where every pack lives. We cover the broader operational version in scaling a letting agency without adding headcount.

    Ten Mistakes That Sink a Rent

    1

    Taking the first three results. Ranking is attribute-matching, not a judgement of comparability.

    2

    Taking the three highest rents. It's the first pattern a tenant's representative checks for.

    3

    A floor area from nowhere. Different sources, different numbers — and a 10% band that silently fails.

    4

    Ignoring BER. It's in the statutory test where it applies, and the Register treats a different BER as a weaker match.

    5

    A different area with no reason. Searching another LEA can be right — but write down why yours had no good matches.

    6

    Stale rents. The RTB asks for the most recent rents. Prefer the newest of the genuine matches.

    7

    No dated printout. The Register changes. Without a record, you can't show what it said on the day.

    8

    Using comparables to beat the cap. Where the old rent carries over, market evidence can't lift it.

    9

    Mixing up the RTB deadlines. One month for a rent setting notice, 7 days for a review. Do both on the day.

    10

    Reusing last year's pack. A re-let in the same block a year on needs fresh comparables, not a copy.

    Where TenantSync Fits

    Full disclosure: this blog is published by TenantSync, and what follows is our product. It's here because everything after the search — the facts, the cap, Part C, Part D, service and the archive — is structured, repeatable work that shouldn't depend on which negotiator did the let.

    Step The risk In TenantSync
    The facts Floor area and BER typed differently each time The Notice of Rent Setting is pre-filled from the lease: address, Eircode, previous and current RT numbers, start date, floor area, BER, last rent and the date it was set, and the agent's PSRA licence number.
    Ceiling 1 A carried-over rent set above the cap The national rent cap is computed from the last rent to the start date, showing which rule applied (2% or CPI) — with a plain warning if the rent is above it, and a note when no cap applies and why.
    Part C Two comparables, or no RT numbers Three comparables by RT number and rent, plus the address for your own reference. Until there are three, the check says so — "You have added 2."
    Part D An exemption claimed that won't stand up Each ground is checked: at least three works for the "other works" ground, the declaration for substantial-change grounds, the reason the last tenancy ended, SSA-only grounds kept to SSA — and a warning when no supporting documents are listed.
    The notice A home-made form missing a field Renders the RTB's prescribed Notice of Rent Setting as a PDF, previewed before it's issued — optionally emailed to the tenants, with the RTB-copy and registration due dates shown.
    The archive The pack lives in someone's downloads Stored against the lease with the exact figures it was rendered from and the cap check in force on the day, so a re-download years later reproduces what the tenant received. Served it elsewhere? Mark it complete and the record keeps who said so, and when.

    What it does not do — plainly

    TenantSync does not search or scrape the RTB Rent Register — you choose the comparables, and the judgement on character is yours. It does not submit notices to the RTB; before issuing, you confirm that the RTB copy is your responsibility, and you upload it through the RTB's Service Centre. Issuing rent notices is on the web app today; the rent-cap calculator and compliance dashboard are also in the iPhone and Android apps. Nothing here is legal advice.

    Frequently Asked Questions

    What is the RTB Rent Register?

    The RTB Rent Register is the Residential Tenancies Board's published register of rents paid on registered tenancies in Ireland. Since 1 March 2026 landlords use it to show that a rent being set or reviewed is not above market rent, by citing three recent rents for similar dwellings in a comparable area, each identified by its registered tenancy (RT) number and rent. It is free to search on rtb.ie by Eircode, dwelling type, number of bedrooms, floor area and BER.

    Do I need three comparables for every new tenancy?

    The RTB's prescribed Notice of Rent Setting has a Part C for three comparable dwellings from the Register, so plan to complete it on every new tenancy. It matters most when the rent is reset to market — a dwelling not let for two years, or a Part D exemption such as the last tenant leaving voluntarily — because then the comparables are the only limit on the rent. Where the previous rent carries over, the national rent cap still governs and the comparables show the capped figure is not above market rent either.

    How does the RTB Rent Register decide what is a match?

    According to the RTB, the Register matches your Eircode to a Local Electoral Area and returns results only from that area — it does not search by distance. It returns up to 10 results, exact matches first: the same number of bedrooms, the same BER and a floor area within 10% of yours. If there are fewer than 10 exact matches, it adds weaker matches — first tenancies that differ only on BER, then those whose floor area is more than 10% away.

    Do I have to use the first three results?

    No. The three comparables do not have to be the first three results. The legal test is dwellings of similar size, bedrooms, type, character and, where it applies, BER, in a comparable area — and the Register cannot filter for character. Shortlist the exact matches, set aside any that are not genuinely similar, prefer the most recent rents, and record a line on why you chose each one.

    What details go on the notice for each comparable?

    For each of the three comparable dwellings, the notice cites its registered tenancy (RT) number and its rent. Keep a dated printout or download of the Register results alongside the notice, because the Register changes as new tenancies register and you may need to show what it showed on the day you set the rent.

    When does the RTB need a copy of a rent setting notice?

    The tenant receives the Notice of Rent Setting at the start of the tenancy. The RTB's current guidance is that a copy must reach the RTB within one month of the tenancy start date. A rent review notice is different: since 14 September 2026 its RTB copy is due within 7 days of the date the tenant was served. The safest habit is to send the RTB copy on the day you serve the tenant. Confirm the current deadlines on rtb.ie.

    What if my rent is higher than all three comparables?

    Then the Register points to a lower market rent than the one you want to charge, and you would need to be able to justify your figure as market rent. A tenant can refer the rent to the RTB, any excess collected can be repayable, and since 14 September 2026 the RTB can issue a €200 fixed payment notice for setting rent above the legal limit. If a cap applies, the cap still binds whatever the comparables say.

    Does TenantSync search the RTB Rent Register for me?

    No. TenantSync does not search or scrape the RTB Rent Register and does not submit notices to the RTB. It pre-fills the Notice of Rent Setting from the tenancy, records three comparables by RT number and rent, warns while there are fewer than three, checks the national rent cap and any Part D exemption, renders the RTB's prescribed notice as a PDF, and stores it against the lease with the figures and cap check in force on the day it was issued.

    Summary

    • The rule: show a rent isn't above market rent with three recent Register rents for dwellings similar in floor area, bedrooms, type, character and BER, in a comparable area — cited by RT number and rent.
    • Two ceilings: the lawful rent is the lower of the cap (where one applies) and what the comparables support. Comparables never lift a capped rent.
    • The Register's ranking: Local Electoral Area from your Eircode; exact = same bedrooms, same BER, floor area within 10%; weaker matches fill thin areas.
    • Choose, don't accept: the first three results are a shortlist. Rule out on character, prefer recent, write one line on each.
    • Deadlines: rent setting notice to the tenant at the start, RTB within one month; rent review RTB copy within 7 days. Do both on the day.
    • Keep the pack against the tenancy — dated printout, reasoning, cap calculation, Part D evidence, the notice as served and proof of service.

    Sources & Further Reading

    The Register and the rules around it are the RTB's. Check every point against the source pages before you rely on it or advise a landlord client.