Expenses incurred in last tax year. Rent in new tax year.

Hi Guys, New to being a landlord, so seeking some advice please on our situation

We incurred ~£3k expenses in Feb / March of 2021 all prior to the tenants moving in. I've convinced myself these are allowable expenses.

Our tenants moved in on the 30th March; which i gather is the date the expenditure would be deemed to have been incurred on the first day of let.

Unfortunately this is only a day or so before the tax year end; and we haven't 'accrued' any rent yet; to offset the costs against.

Any ideas on whether we are able to include for these expenses in tax year 2020/21; despite only 2 days worth of income !

Hope this makes sense and someone can point us in the right direction please.

Thanks  !