One of the nominal accounts in the import has the Compulsory Costing flag set in the Details tab. Clear this flag, or enter costing details in the import, to continue.
Use Access Office Integration to identify which code is generating the error. The Compulsory Costing field in the Nominal Accounts template shows records with this setting enabled.
If the error appears in DataHub, review the transaction details in the Messages area to identify which nominal accounts are being updated.