Navigating Tenant Move-Out Dates and Valid Notices

Hi,

Our AST says when a tenant serves notice to move out, the notice date is one month from the rent date.

The rent date, in this case, is the 5th of the month.

We are beyond the minimum term and are rolling forward month by month.  

Making a date as per the AST 4th of May as he has just served notice on the 23rd of March.

He has requested to make the termination date 23rd April. (he is moving to a larger home). We want to accept as we have another tenant who wants to move in on 24th April.

All would sound well under this arrangement, except the current tenant's new home has fallen through. (he has a habit of putting on low offers for apartments and then losing the deal to other interested parties).

I am worried he will not agree to an AST in time with another apartment.

My question is:
 
If we accept the 23rd of April as the move-out date as he has requested (so both parties agree), does he have any right to change the move-out date to the 4th of May, as that's the notice period specified on the AST?

I don't want to commit to a new tenant and risk leaving them homeless.

View Related Handbook Page

Tenant Wants to Leave

A periodic tenant intending to leave must provide a notice to quit in writing. The minimum notice period is four weeks (specified in section 5 of the Protection from Eviction Act 1977). The length of the notice should be at least the length of a rental period (subject to the four-week minimum rule and up to a maximum of six months). This will be a calendar month for a calendar monthly rental in most cases. Where the rent is quarterly, a quarter's notice is required, six-monthly or yearly requires six months' notice. The notice should always expire at the end of a rental payment period or the first day of a new period.