The concept of a SME is at best vague, at worst completely meaningless. In the USA it is not used particularly often when reffering to bussineses, the term SMB being more popular. So it was to this end that the European Union decided that, within the EU anyway, it will be best if there is some kind of harmonisation so that there is a level playing field.
The main recommendations that were brought up were that companies with fewer than ten staff members ought to be regarded as micro businesses, fewer than 50 they are categorised as small, and those with fewer than 250 are to be regarded as medium sized. The main reason was beacause there variations in the definitions and in the tax rates across the EU, and it was leading to there being unfair advantages for some countries' SMEs over their neighbours.
So there it is now you know where your business stands, at least in the EU, but that is better than nothing.
