As a starting point, use the number of routes your business will manage, how many drivers you will have per route, and expected weekly pay per driver on that route.
For illustrative purposes only:
Your business has 5 routes. You plan on using 2 drivers per route at £15 an hour. You expect to pay each driver £825 per week.
£825 x 2 (drivers on each route) x 5 number of routes = £8,250 in weekly driver payments.
£8,250 x 52 = £429,000 in annual payment for drivers and helpers.
Your business may also have clerical and owner payments to consider when reporting.
It is important you report your projected driver(s)' payments accurately as under or over reporting can affect your insurance policy.