The form depends on the sector
A private landlord uses Form 4A. Form 4 is for social landlords. The builder selects on that basis rather than offering both and hoping.
The timing
One increase in any 52-week period, with the notice given far enough ahead that the tenant has time to respond. The builder prints the earliest date the new rent can start, so you are not calculating it from the tenancy start yourself. Choose the property and the builder fills in the tenant names, the tenancy start and the current rent from the tenancy.
The new rent reaches the rent
For a monthly rent, tick Bill the new rent from that date and the notice does more than sit in a folder: when you download it or email it, the new rent is scheduled on the tenancy, and the rent charges and the Direct Debit move to it from the start date. Every emailed or downloaded notice is recorded, so the rent page knows when the rent last changed.
If the tenant challenges it
A tenant can refer the proposed rent to the First-tier Tribunal before the increase takes effect. That is their right and it is not a sign anything has gone wrong. If they do, or if you decide not to serve the notice, cancel the scheduled change under Scheduled rent changes on the same page and the rent stays as it is. The notice, the date it was served and the figures are all in your activity log if you need to show what was proposed and when.
Contractual rent review clauses
Do not rely on one. The statutory route is the route, and a clause in an old agreement does not substitute for a properly served notice.
The council average on the rent review board
In your own account, the rent review board shows, under each rent, the Office for National Statistics’ average monthly private rent for the council area and the number of bedrooms, with the month it is for. It is the council average for all private rents, across new and existing tenancies, not the market rent for your home.
It shows for whole homes with one, two or three bedrooms, in the councils in England and Wales that ONS publishes, once the property’s number of bedrooms is recorded and its postcode has been looked up. Section 13 comes with paid plans, and the board in an agency workspace does not show it.