The department failed to reply within the allotted 20 working days to the request by Third Sector under the Freedom of Information Act. It was then given another ten days by the ICO but still did not respond.
Jenny Manock, casework manager at the ICO, told Third Sector: "As the Cabinet Office has not responded in accordance with our instructions, our next step will be to pass your case to our complaints resolution department, who will investigate the reasons and look to issue a decision notice."
A decision notice is a legal order requiring a public body to address its failure to answer a request made under the act.
An ICO spokesman said: "If they do not adhere to the order they are breaking the law and it then becomes a matter for the courts."
A Cabinet Office spokeswoman said it had nothing to add to previous response saying it was still looking at the request and would respond to it in due course.
The request on 3 March asked how many OTS staff had received bonuses in the past three years and the total value of the bonuses each year. The OTS, which employs about 60 staff, is part of the Cabinet Office.