Hi there - depending on the software you are using, you could create and entry for the £100 tax deduction and code it to the nominal code set up for CIS tax deducted from Sub-contractors. I have a small builders business on my books who doesn't have any CIS add-ons and I find the easiest way to deal with sub-contractors is to post the sub-contractors invoice to the purchase ledger personal account. When the invoice is paid (less tax) allocate the net payment to the invoice, leaving a balance which should be the amount of tax deducted. The software we use has an adjustment function so I use this in effect to create a credit note, which is coded to the CIS tax code and then match the invoice, payment and tax deduction in the personal account thus squaring everything off and getting the tax amount in the correct nominal.