Here is the Association of Chartered Certified Accountants guidance for the assistance of students [edited]:
'PRE-VAT REGISTRATION EXPENSES AND ADMINISTRATION
One of the key questions businesses ask in VAT registration situations is regarding pre-registration input tax recovery.
There are separate rules for goods and services. For goods to qualify for input tax recovery they must have been purchased for the purposes of the business and not supplied onwards or consumed before the date of registration, and finally the VAT must have been incurred within four years of the date of registration.
For services for qualify, the cost must have been incurred for business purposes and the VAT must have been incurred within six months of the date of VAT registration.
In both situations the input tax recovery is subject to being supported by an appropriate VAT invoice. Also, the input VAT would be claimed through the businesses first VAT registration.'
cfg.ord gives the following advice which is perhaps more comprehensive:
You can recover input VAT on pre-registration purchases for:
• Goods that have been purchased for taxable activities and are still
‘on-hand’ at the date of registration (for example as fixed assets or
stock), providing they were not purchased more than four years prior
• Services supplied up to six months prior to the date of registration.
The services must have been supplied for a taxable activity and not
re-supplied before registration'