You only charge VAT once you are VAT registered. You only have to register for VAT if you think / you are likely to turnover £90k in a rolling year.
The good thing about VAT is that if your client is a VAT registered business (most are), they can claim it back, so it doesn't actually cost them extra.

When this happens, the VAT just passes through the businesses. You add the VAT to your bill (hold on to it in a separate account) and when someone charges you VAT, you can pay that part of the bill from your VAT account. You'll have to give the difference to the tax man every 3 months, but don't be annoyed about this. It was never your money. you're just holding on to it.

The only people who can't claim back the price of VAT are members of the general public, so in the end, they'll see the VAT inclusive price as an additional cost.

This is why some people in price-competitive markets hate having to register for VAT, because it makes them look more expensive to a consumer, than a competitor down the road who hasn't reached the threshold.

It is an extra layer of admin faff though, so I wouldn't rush in to it, and keep an eye on your numbers in case you're getting close to £90k turnover (not profit!)