If you are not able to match or verify your subcontractors automatically you can add in the verification code (obtained from HMRC) for the subcontractor manually.
Navigate to the Tax > CIS > Verification menu.
Click on the link within the text To manually enter a verification code click here.
Enter the verification in the box beside the appropriate subcontractor and hit the Update button.
Please Note: Manually verified subcontractors will not show a tax treatment, so please make sure to be using the correct CIS deduction rate when creating bills for the subcontractor.