The time to submit a claim is at the end of each tax year. The details of the claim and reason for overpayment will need to be submitted along with the form P35. (which shows the total CIS deductions made from the company in the tax year).
HMRC aim to process claims within 15 working days if the claim is straightforward. Payments are made no earlier than 2 weeks after 19th May to ensure the majority of P35 forms have been received and processed.
CIS deductions are not transferrable between sole-traders, partnerships and companies. If you have been paid as a sole-trader or partnership, then those CIS deductions cannot be claimed by the company. The income and deductions are shown on your Self Assessment return for the year instead.
The online leaflet also includes details of helplines, CIS website and information on Payment and Deduction statements.
Please see link:http://www.hmrc.gov.uk/cis/cis-qanda-article.pdf