Effectively as I'm not salary sacrificing I'm increasing my 'salary' by the value of the car (vs using my salary to purchase a car personally, as I did with my current car), minus BIK which is zero/minimal, plus the added advantage of offsetting corporation tax.
Well, as the business owner although you might not describe it as salary sacrifice the situation is very similar - if you were previously taking all the spare profit out of the business as salary, you will now have to take a bit less salary so the business can afford the car, so it's salary sacrifice in everything but the name. The situation is a bit more complicated as the business owner has the option to take profit out of the business in ways other than salary (dividend for example), so it's not quite so simple as the employment case where you can directly compare the income tax +NI on the salary needed to pay for the car vs income tax and NI on the BIK notional amount. However, one way or another the profit has to leave the company or get spent on providing a benefit in kind.
If we are trying to look at the whole picture, then there's a few other things to take into account.
VAT: except for special cases (driving school car etc.) the business does NOT recover VAT on the purchase of the car, but does not need to add VAT when the car is sold, so that's exactly the same whether the car is owned privately or as a company car. The business (if VAT registered) can recover VAT on maintenance costs (tyres, repairs etc.) so that's a small additional saving for the company car case.
Business mileage: perversely, having the car as a company car becomes less attractive if you do significant business mileage (not commuting). On a private car used for business, the company can pay the 45p rate (25p after 10K miles) free of income tax/NI - and if the company is too mean to pay it all, you can claim back income tax on the difference between 45p and what they actually paid. The generous-looking 45p is meant to pay for the whole cost of providing the car, not just the petrol. For company car used on business, they can only pay the actual additional cost of fuel which is much less. With next year's 0% BIK, the company car will almost certainly win regardless of business mileage; in future if the BIK goes back up then it might become better owning privately for people who do high business mileage.
How to claim for business mileage is also a factor. For the privately-owned car this is straightforward: everybody gets the same rate (45p/mile up to 10K then 25p/mile) - and this is fair because it's meant to cover the whole car cost; EVs cost less for fuel but more for the initial capital cost so it's equitable to pay everybody the same rate. Watch out for this if an employer tries to pay a lower rate for privately-owned EVs "because your fuel is cheaper" - they are being unfair (but at least you can get the tax bit back).
For company cars they are just reimbursing the marginal costs - primarily fuel - tax free but only to cover the actual cost incurred. The employer can pay for all your fuel, but then you pay a further (large, arbitrary) BIK charge to cover your private fuel, so most people don't do that (and you can't for EVs anyhow - see below). So in the normal case, the employer is supposed to be reimbursing the employee (as "expenses") for the additional costs of running the company car on strictly business journeys (not commuting). For ICEs, it's impractical to slice up the actual cost of a tank of petrol into which bit was business and which bit was private, so normal practice is to pay a mileage rate for the business miles (HMRC specify
advisory rates varying for fuel type and engine size, but around 10p/mile). Employee pays out of his own pocket for all the fuel going into the car, keeps records of all the miles traveled on company business, and then gets paid tax-free expenses for that amount. For a long time, HMRC didn't publish an advisory rate for EVs, arguing that you don't need it. Eventually they were persuaded to do so, and it's now 4p/mile. However, I suggest that it's not actually sensible to use this for most company EVs, because extra costs are very variable: charge at home on E7 and it can cost you only 2p/mile, charge at an Ionity public charger because it was the only practical option for your business journey and it can cost you over 20p/mile!
HMRC have said that "electricity is not a fuel" for the purposes of the special private fuel BIK rules - but that doesn't mean that that an employer can give you unlimited free electricity, just that electricity is treated like any other BIK (health insurance, gym memberships, etc) so that it is taxable if used other then for business purposes. However, there are some special exemptions: employers can provide free workplace charging even for private EVs and even for private use without incurring BIK.
So I would suggest that for most company EVs with moderate business mileage a sensible approach would be to just claim for actual costs of public charging (including supercharging) when required to travel on business, and not bother to keep track of mileage. You lose out on short business trips where you just charged at home, but the cost is trivial - do you really want to spend time keeping records of all your mileage just for the sake of a £2 claim on a 100-mile trip? If there's a chargepoint at the office, then you are still winning overall.
