So my mum has some properties she rents out but she’s been very old school and not taken deposits or given tenancy agreements and most of the tenants have been in the properties for a long time.

She’s now getting on and has finally decided to let me manage them and I’m looking to do it properly.

So I’ve managed to sort 3 places out with new tenants and proper agreements and rents etc. but there’s 2 left that I’m unsure on how to approach as the tenants are already in.

1 has been there for about 10yrs or more and only pays £550pm for a property that should be getting twice that in rent.

The other has been in for a couple years and is only paying £500pm when the rent should be £750 (this is a flat and worth noting that the other flat in the building she owns I’ve rented for £675)

I’m not looking to be an asshole landlord and want to keep the rents affordable but as in the £550 should increase to £875 like the other houses we own on that street and rent out and the flat as mentioned above and will increase to £675pm

So I’d like to know how to go about this and provide an actual tenancy agreement to them and go be them an increase in rent. Also how much notice do I need to give to them for the increase?

I just want to avoid any hassle due to her being old school but need to bring it into modern times and get it done properly too.

Any help would be appreciated (England)