At the beginning of Henry IV's reign the Hanseatics were advised that their privileges should be enjoyed only by those merchants and shippers who bore sealed letters of identification from their native towns. To what extent, if any, this rule was enforced is not known, although compliance ought to have been a relatively simple matter. During negotiations early in Edward IV's reign the king's lawyers ruled that only members of the London Gildhall were entitled to use the franchises. This was probably a device to restrict the number of provincial merchants who escaped payment of tunnage and poundage. Everyone claiming immunity now had to be certified by Gildhall officials as a member of that organisation. The check continued until at least the reign of Henry VIII, and there are many surviving certificates from throughout the period. They were sent up to the Exchequer by the customs collector with his particulars of account to establish the claim for allowances. Anomalies in the dates of some of the earliest certificates raise doubts about the integrity of those operating the system. The first is addressed to the customs collectors of Hull from the alderman and merchants of the Gildhall, and was allegedly sealed by them on 9 July 1463. The certificate names seventeen men but gives no details of their trade, and was returned to the Exchequer with the relevant particulars of account and a separate, undated schedule of another nineteen names, this time with the value of each man's goods.