Raising the rent used to be a quiet job. A letter, a chat, maybe a clause in the tenancy that did the work for you. Under the Renters' Rights Act, that world has gone. There is now one legal way to raise the rent on a tenant, and if you wander off it, the increase can be challenged and stalled. Worth getting right, because most landlords do this every year without thinking.
Here is the shape of it now.
All tenancies are periodic, and any old rent-review clause in the agreement no longer does the job. You cannot rely on "the tenancy says I can put it up in April". The only route is a formal notice, the Section 13 notice, on the prescribed form. Get the form wrong and you have not really served notice at all.
You can only do it once in any twelve months. Not twice, not "a bit now and a bit later". Once.
You have to give at least two months' notice before the new rent starts. That is longer than the old one month, so build it into your timing.
And the figure has to be the market rent, what the place would actually let for today, not a number you would like. Push it above the market and you are handing the tenant a reason to fight it.
That is the part landlords miss. The tenant can refer your increase to the First-tier Tribunal, for free, before it takes effect. Two things follow. The increase does not start until the tribunal has ruled, so a challenge buys the tenant time at the old rent. And the tribunal cannot set the rent any higher than the figure you asked for, only the same or lower. So an over-ambitious number has no upside and plenty of downside.
So here is how I run a rent review now, and how I would suggest you do too:
Check the real market first. Look at what similar places nearby are actually letting for this month, and set your figure at or just under it. A defensible number rarely gets referred.
Use the correct Section 13 form. Not a letter, not an email, not the old rent-review clause. The prescribed form, filled in properly, dated properly.
Count the notice properly. At least two full months before the new rent starts, and never more than once in twelve months.
Talk to the tenant first. A quick, human heads-up before the formal notice lands takes the shock out of it, and a tenant who understands the number is far less likely to run to a tribunal.
Keep the copy and the proof of service. If it is ever questioned, you want to show exactly what you served and when.
From my own portfolio: My rule is that a rent rise should be boringly correct and never a surprise. I set it at the market, I tell the tenant it is coming before the form arrives, and I serve it clean with two months to run. Done that way, I have never had one parked at a tribunal, because there is nothing to argue about. The landlords who get into trouble are the ones reaching for a number the property does not support, on a scrap of paper that is not the right form.
The temptation, when costs are up, is to push hard on the one lever you control. I understand it. But an increase that gets referred and frozen earns you nothing for months, and sours the relationship on top. A fair increase served properly beats an aggressive one that collapses.
The takeaway: one route only, the Section 13 form. Once a year, two months' notice, market rent, no higher. Warn the tenant, keep your proof, and set a number you can defend. Do that and the rise just happens. Overreach and you hand it to a tribunal.
If you know a landlord still relying on the rent-review clause in an old tenancy, tell them. That clause is not going to work any more.