Yes. You can normally arrange cover before trading begins, but the proposed business use needs to be described accurately. The important point is to make the policy describe the real arrangement rather than the simplest answer on the form.
Why this can be an insurance issue
A new sole trader may buy a van before the first customer arrives. Insurers can quote on the intended occupation, mileage and use even though the business has little history.
Motor insurers price a bundle of facts together. A detail that looks minor on its own can matter because it changes who controls the vehicle, where it is kept, how often it is driven or what the insurer may have to pay after a claim. That is why two insurers can react differently to the same situation.
What to put on the quotation
Give the realistic start date and intended trade. If your work changes quickly after launch, update the policy.
If the online form does not give you an answer that truthfully fits the situation, do not force the nearest convenient option. Complete as much as you can and check the point with the provider before buying. Keeping a note or email confirming an unusual arrangement can be useful later.
What can go wrong
Do not choose private use simply because the business has not yet issued its first invoice.
The problem with an inaccurate answer is not merely that the premium might have been different. If the undisclosed fact is relevant to a later claim, the insurer may investigate whether the policy was written on the correct basis in the first place.
Will every insurer treat it the same way?
No. Underwriting rules differ. One provider may accept the arrangement with no difficulty, another may charge more, and another may decline to quote. That variation is one reason a comparison can be useful when your circumstances are a little outside the ordinary.
Before you buy
Read the main policy information and check the excess, level of cover and any condition connected with the unusual part of your situation. A cheap quotation is only useful if the policy actually reflects the way the van is owned, kept and used.
See how different insurers respond
Enter the details as they really are and compare the quotations and policy terms offered for your circumstances.