New RTB Rent Calculator: another twist of the knife against accommodation providers?

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stormy

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Has anyone else noticed the calculation logic in the new RTB Rent Calculator (released March 1)? It appears to be designed in a way that effectively robs providers of one month of inflation during annual reviews.

The Issue: Misaligned Benchmarks
I conduct an annual rent reviews on March 15th every year.
  • Last Year (March 15, 2025): The March CPI index hadn't been published yet. Any compliant provider, could only have used the most recent data available at the time: February 2025 (101.5)
  • This Year (March 15, 2026): The most recent data available is February 2026 (104.2).

Basic Maths
To capture a full 12 months of inflation, the calculation should be:
  • Correct Calculation (Feb26 vs. Feb25): 104.2/101.5 = 2.67%
However, the RTB calculator automatically pulls the index for the month of the review, regardless of whether that data was actually available to you when you last set the rent.
  • RTB Calculation (Feb26 vs. Mar25): 104.2/102.2 = 1.96%

The Result
Because the RTB uses the March 2025 index as the starting point (a figure that wasn't even public on March 15, 2025), they are only measuring 11 months of inflation for an annual review.

If this logic holds, every "annual" review done through this tool will permanently lag behind actual CPI (as tool measures "annual" over 11 months!)

A mistake? At this stage, I highly doubt it.


Notes
  • I know we have moved from HICP to CPI, but logic remains the same - base level should be index level available at the time
  • I know these are all capped at 2% etc, but anyone doing a review this month is not getting the 2% they are entitled to

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The exact same happened to me and I phoned the RTB on Wed this week to look into it further for me.

I set my rent 3/3/26 and the register pointed to Jan Cpi. 103.3 which limited my rental increase to just €13.
I did all the paperwork and uploaded to RTB and gave tenant 3 months notice.

I went in to the register this week and put in the 3/3/26 again and this time points me towards Feb cpi figures.104.2 which now would have allowed an increase €23.

I spoke at length on the phone and explained that when I go in on 3/3/27 next year the RTB calculator now assumes I am comparing the CPI in March 27 to 104.2 from the previous year.
And therefore assumes ( in error ) I got €23 increase this year.

I asked her to speak to her colleagues on this and tease it out and revert back to me - I have heard nothing back yet.

By using the 104.2 for rent setting in 2027 as the previous year comparison in my case will be an error because I was limited to work of the 103.3 this year -therefore my point was I should be able to use the 103-3 next year as my comparison.

I explained that any rental increase are already very minimal without being cut further.
Whilst it is only s few € and not a lot in the scheme of things and not even worth the time and effort involved in all the paperwork
- it is the principle here that their rent register can deny valid increases.

I did explain all my paperwork has been uploaded to them to check it if necessary and the CPI used in my paperwork in March 2026 should be the exact same CPI that I will be allowed to use as a comparison in March 27.

I did say to them to check this out because many others will be ringing them and they will have the exact same problems with this unfairness in the system.
 
Interesting. So thats even worse then depending on your last set date. If your prior set date was, say, 3 March 2025, then you would have had your annual inflation measured over just 10 months! Base level for last setting would Mar25, and base level for new setting would be Jan26!

It would be farcical if it all wasn't so serious.
 
I've noticed another significant issue with the RTB calculator. This time on how it interprets the 2% cap. For this 2% cap, the legislation limits increases based on the 'proportion that that period bears to a year.' However, the RTB calculator rounds down to the nearest full month, completely ignoring partial months.

For example, if your last rent set date is 1 Feb 2025 and your new date is 28 Mar 2026, the calculator only credits you for 13 months (13/12 * 2% = 2.167%), entirely discarding the extra 28 days in March 2026. A true, fair pro-rata calculation should be done daily, giving you (420 days / 365 * 2% = 2.3%).

By interpreting the Act in whole months, the RTB is structurally disadvantaging accommodation providers on almost every calculation. The prior version of the calculator did it daily (which is fairer and inline with a reasonable interpretation of the Act). The new version of the calculator disadvantages the accommodation provider.

It's yet another example of the bias of the RTB and their penchant to penalise those providing accommodation.



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Note: There is no compounding in my calculation above, but at least this is not an RTB issue as the legislation is specifically worded not to allow for compounding of the 2% cap.
 
stormy said:
Note: There is no compounding in my calculation above, but at least this is not an RTB issue as the legislation is specifically worded not to allow for compounding of the 2% cap.
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Not doubting you @stormy but is that correct - the 2% cap now doesn't compound?

That is crazy because inflation certainly compounds!
 
Greenbook said:
Not doubting you @stormy but is that correct - the 2% cap now doesn't compound?
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It never did. The legislation is worded as such. The end of this post below shows the old calculator also didn't compound the 2%



My point above is probably more serious though. It shows that when the 2% should be calculated over 13.9 months, they have calculated it over 13 months. The RTB it upon themselves to implement this logic though as the legislation doesn't say it should be calculated like this.

Yet another example of anti accommodation provider bias.
 
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Just to be clear, if you do annual rent reviews, it will work out that you will get the benefit of compounding. However if you did rent reviews say once every 10 years, instead of having the cap at [(1.02^10)-1]= 21.9% it's actually 2%x10=20%
 
If they are rounding down, so you get 11 months of rise for 12 months of time, then it acts as an anti-compounding effect.

Twice in 2 years gives 11/12 months, so 1.83% per year, so 3.69% for 2 years.

Once in 2 years gives 23/24 months, so 3.83% for the 2 years.

You are better off doing it every 2nd year.

Since the landlord can choose the date, the best strategy would be to do the rent review every 12 months and 1 day. Landlords who don't know that would get burned.
 
LarryScott said:
Since the landlord can choose the date, the best strategy would be to do the rent review every 12 months and 1 day. Landlords who don't know that would get burned.
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This is not clear under current implementation by the RTB. E.g. do this today. Last set date = 28Mar25, setting date of today 29Mar26. You are not capped by the 2% but the inflation. Issue is that the inflation is measured from 31Mar25 to 28 Feb26 (i.e. "annual" inflation measured over 11 months, even though it's over 12 months since the last set date).

This was the point I was raising in my original post.
 
LarryScott said:
Would it be possible to take the hit for 1 year and then align all the dates, so you get almost the full amount each year?
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I don't believe so. If the current logic stays in place, for one carrying out annual rent reviews (even if 1 year plus 1 day) then the annual inflation is always measured over either 11 months or 10 months (if your latest date falls before the CPI index level is published for the prior month, see @Millie* post #2 above)

Let me know if someone figures out a work around but it looks to me they've made it much harder, if not impossible, with this new calculator to get either the allowable 2% or the full 12 months of inflation.
 
@Millie* - you are exactly right, if you do an annual rent review early in the month (i.e. before that's months inflation figures are released), the RTB count annual inflation over 10 months!!

Example below:
Date Last Set: 1Apr25
Date New Set: 1Apr26

Last Inflation Index Level taken as of 30Apr25
New Inflation Index Level taken as of 28Feb26

30Apr25 - 28Feb26 = 10 months

Extraordinary stuff. I should be shocked the RTB can get away with things like this, but at this stage one would not even know where to start with all the anti accommodation provider bias at the RTB. As a reminder, the prior version of the calculator, did not do this - it at least calculated inflation (and the 2% cap for that matter) correctly.

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stormy said:
As a reminder, the prior version of the calculator, did not do this - it at least calculated inflation (and the 2% cap for that matter) correctly.
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Are you sure of that? I had the issue several times before when the index wasn't out and so the rate of increase was lower than could have been.
 
Premos said:
Are you sure of that? I had the issue several times before when the index wasn't out and so the rate of increase was lower than could have been.
Click to expand...

For the ones I checked yes. Checked several of my reviews from the past and they were all as expected.


If the current index isn't available that's understandable, it uses latest version available. But, in old calculator, for prior period it used index level that was available at time of setting, hence at least annual inflation was measured over 12 months.

In this version of the calculator, it's using a prior index level that wasn't even published at the time of prior rent review.
 
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