Essentially if you get a car with under 110g/km of CO2 - which essentially means you buy either a rubbish car OR a BMW 320d EfficientDynamics (I'm not saying that the only non Rubbish cars in the universe are those too, just that it is the only normal car that have managed to get under here) before 1st April 2013 you can claim a 100% Writing down allowance in Year 1.
What this means is that you can offset the
entire cost of the car against your companies profits for tax purposes. I'm sure you know what this means but lets imagine your company reports 100k profit which is then taxed at 24%. You'd pay £24k and end with net profit after tax of £76k.
But you buy a 320d ED for £28k. Your profit for tax purposes is now £72k. So you only pay £17k @ 24% saving £8k on tax.
This is a huge saving and makes buying the brand new car a no brainer, you effectively reduce its net cost to £20k which is a bargain for a brand new 3 Series.
This assumes you only use the car for business purposes. Which you probably don't, so its best case scenario. What actually happens is that you only get the WDA on the percentage the car is used for business in that tax year. So if you use it for 50% business, you get 50% of 100%.
Now of course it isn't THAT long to the end of the tax year by the time the car arrives so of course it is your choice how much you use it for personal usage in this tax year
Don't forget you'll then be driving the car as a company car so you'll be liable for company car tax. If you are a 20% taxpayer (Which as a hard working director of his own limited company who obviously will not want to draw a massive salary I'm sure you will be...) this is £70 a month.
The savings are much lower though if you don't pay full corporation tax - ie you take under 300k a year of profits - as your tax rate is lower. If you pay that rate, I reckon the difference between buying it yourself and buying it through the company is much smaller (£5.6k saving using my example of 100k profit). The lower your profit the lower the saving and the less worth the bother it all becomes.