Selective licensing when a property is vacant

I have recently discovered that my property requires licensing as i fall under a selective licensing scheme. This was introduced just under 6 months ago, and I have just been contacted by the council's enforcement team, who have also demanded a further £150 finder's fee.
My tenant has just vacated the property, and my property may be vacant for 4-6 weeks.
Am i under obligation to obtain a license while my property is vacant? - technically i am not renting at the moment but of course that may change soon however i accept i was in breach of this law for around 6 months.

If i delayed this license application till i get tenants, would i then need to pay this finder's fee and late charges?

Many thanks