Pre-trading expenditure
Those expenses incurred by your company after it was formed but before it started to trade.
The tax position in this case is fairly straightforward. If this expenditure would have been allowable if the company was actually trading at the time, then the company can claim a tax deduction for it in its first accounting period. You can see how this set out in the tax rules here.
You can also claim VAT on pre-trading expenditure provided the VAT you are claiming meets the usual rules re pre-registration and having a valid VAT invoice.