Uk cis

I have a customer who needs to report CIS on 3 of their companies. I have the document for VAT Domestic Reverse Charge for CIS but this does not appear to account for a supplier who is Zero Rated for VAT but is subject to CIS tax on any labour that they carry out on buildings.
The supplier is setup as Zero Tax Liability. Their invoices can have a couple of lines, i.e. for materials and labour. The Materials needs to follow the Zero VAT rated process but the line for Labour needs to have 20% CIS Tax deducted at Payment time.
The issue I have is that the “Witholding Tax” is held on the Tax Type and I don’t know how to pull that through to an invoice line.
Any ideas greatfully received.