https://www.slab.org.uk/guidance/information-you-should-retain-to-vouch-for-your-accounts/
Assessing accounts and subsequent taxation before the auditor, if the process reaches that stage, is an objective exercise requiring the justification of the work undertaken. For example, you must
To ensure we deal with accounts promptly, it is essential that you send us all outlays vouchers (including counsel’s fees, where appropriate). When submitting a paper account you should attach all increase forms securely to the account.
For online cases you do not have to send us the increase forms, as the information is available on the system. To claim outlays using the online system, you should email us scanned vouchers, or send us the paper copy, using the printed attachment barcode, so that we can scan it and attach it to your online account.