Yes, as a start-up, you can providing the expenses were made for business purposes. These expenses will be treated as though they were incurred on the first day of trade and tax relief will be given where appropriate.
VAT can also be reclaimed on these business expenses made prior to the date of VAT registration – the rules for this are different for goods and services.
You can go back up to four years from the date of registration for VAT on goods you still have on hand or that have been used to make other goods you still have.
It's six months for services.