You can only attach a file to a National Audit Report & to an Audit Control Report when first the OPs have been identified under the 'Programmes covered' section.
The reason is because as long as there are no programmes covered by the NAR & ACR, the system cannot apply document security based on the Funds covered by these Programmes and therefore requires you to have the document update permission for all Funds.
Thus you must first specify the Programmes covered and then you can create documents for your Funds.