The documents in this series contain very detailed information on the collection of customs in English and Welsh ports, including the ancient custom, the new custom, the mutuum, the subsidy, tonnage and poundage. There are also details of the seizure in the ports of money, provisions, cloth, arms and horses, intended for illegal export, and thus forfeit.
Included in the series are three types of documentation: the particulars of account, compiled by the collectors of customs; subsidiary documents, such as receipts and vouchers, to support the collector's account; and the accounts for audit drawn up at the Exchequer. Some particulars and subsidiary documents still survive in their original leather bags.
After 1565 the series contains only the subsidiary documents: files of cockets, notes of seizures, tunnage rolls and views of accounts. The accounts proper were by this time written up in the port books.