The rent review notice: 90 days and three comparables

A rent review notice must give you at least 90 days before the new rent starts. It must be in the form the RTB prescribes, and it must come with two attachments: the RTB rent calculator printout and three comparable tenancies from the RTB's Rent Register. A copy must reach the RTB within 7 days of service. A notice that misses any of these may be invalid, and a defective notice does not change the rent.

The 90 days answer the question people type most: how many months' notice for a rent increase. It is a little under three months, counted from the day you receive the notice. The rent increase checker counts them for you, checks the figure against the cap, and gives you the last day to refer a dispute.

What the notice must contain

Section 22 of the Residential Tenancies Act, as amended from 1 March 2026, sets the contents.

The notice must also keep to the cap. A perfect form with a figure over the lower of 2% and CPI is still over the cap. The 2% or CPI cap gives this month's figure, which is 2% while the CPI runs above it.

The 90 days and how to count them

The 90 days run from the day the notice reaches you to the day the new rent starts. The new rent cannot begin earlier. A notice served on 27 October 2026 cannot start a new rent before 25 January 2027, and a notice that names an earlier date may be invalid.

The date of service is the day you received the notice, not the day it was written and not the day it was posted. If it came by post, write down the day it arrived. If it came by email, the email carries the date. Keep the envelope or the email in your tenancy file.

Two clocks run at once. The 90 days are the notice period. The 12 months since the rent was last set are the review frequency, and the new rent cannot start until they have passed too. Where your area became a Rent Pressure Zone within two years before the rent was last set, that period is 24 months. The checker dates both.

The three comparables

The comparables are there to prove market rent. The Act requires three tenancies from the RTB's Rent Register that began within the last three months, in homes of similar floor area, number of bedrooms, type, character and BER, in a comparable area.

Read them against your own home. If the three are all two-bedroom apartments and you rent a one-bedroom flat, they do not compare. If they began a year ago, they are stale. If they are in a different kind of area, they say nothing about yours. The Rent Index guide and the county pages carry the RTB's published averages, which give you a sense of whether the comparables are plausible.

Market rent is a ceiling, not a floor. Even where the comparables show a higher market rent, the increase is still capped at the lower of 2% and CPI. The comparables matter most where the landlord argues that the capped figure is itself above market, which would bring the rent down, or where the landlord claims an exception.

The copy to the RTB

Since 14 September 2026 the landlord must send the RTB a copy of the review notice within 7 days of serving it on you. Between 1 March and 13 September 2026 the copy had to go the same day. The copy is part of what makes the notice lawful, and a notice whose copy did not reach the RTB in time may be invalid.

You can ask the RTB whether it received a copy. The RTB copy rule guide explains how to ask and what to keep.

Service by post is still allowed for a rent review notice. The RTB's advice to use email or hand delivery, which followed Argutinski v RTB, is about notices of termination, where the date of service decides the whole timetable. A posted review notice is served when it reaches you, so the 90 days run from that day.

What makes a notice defective

A review notice may be invalid where it:

• gives fewer than 90 days before the new rent starts;
• starts the new rent less than 12 months after the rent was last set, or 24 under the transitional rule;
• raises the rent by more than the lower of 2% and CPI, or above market rent;
• is not in the prescribed form, or is unsigned or undated;
• has no RTB calculator printout, or no comparables, or comparables that are not comparable;
• did not reach the RTB as a copy within 7 days.

A defective notice does not change the rent. The landlord's course is to serve a fresh notice that meets the Act, which starts a fresh 90 days. Only the RTB can decide that a notice fails, so the safe course is to refer it rather than to ignore it.

What to do when one arrives

Keep paying the current rent. Do not pay the new figure before the date it lawfully starts, and do not stop paying because the notice is wrong. Arrears would give the landlord a ground they did not have.

Run the notice through the rent increase checker. It checks the figure against this month's cap, counts the 90 days and the 12 months, and gives the last day to refer a dispute. Run the same dates through the RTB's calculator and keep the printout.

Ring Threshold on 1800 454 454, Monday to Friday 9am to 9pm, with the notice in front of you. If the notice is wrong, write to the landlord first; the letter builder has a letter that sets out the defect and asks for the notice to be withdrawn or corrected.

If the landlord does not withdraw it, refer a dispute to the RTB at least 28 days before the new rent would start. The review is paused while the dispute runs. Challenging a rent increase at the RTB takes you through the application and what the RTB can order.

Where this leaves you

A rent review notice has a list to pass. The prescribed form, signed and dated, the old rent and the new, and a start date at least 90 days away and at least 12 months after the last setting. Then the calculator printout, three fresh comparables, and a copy to the RTB within 7 days. A notice that fails the list may be invalid, and only the RTB can say so. Your part is to count the days, check the figure, keep paying the current rent, ring Threshold, and refer the notice in time if anything is wrong.