Why is the new mileage module only available for sole traders and partnerships? Most of my sole traders and partnership clients don’t claim mileage, they claim actual costs and add back private usage. In fact its my limited company clients that claim mileage to avoid benefit in kind costs.
I therefore think you need to rethink that policy.
The new mileage module has been designed specifically for businesses using the "Simplified Expenses" scheme which is not available for use by Limited Companies. We are planning to widen the scope of the Mileage module to make it suitable for Limited Companies in a future release.