Hi again.The accountants are probably referring to potential capital allowance claims for plant and machinery and integrated features in a commercial building used in your business which you can read about here and here. See under "Fixtures in buildings" and under "Integral features of buildings" when you click on the first link.Look under "Claiming" here and here for more detailed descriptions of the types of things you can claim for. The first one was written by a firm which specialises in making such claims and with which I have no connection. I also have no connection with the other firm.
Any claims can be made though your CT600 corporation tax return as part of your regular capital allowances claim. Expect HMRC to ask questions and have detailed calculations prepared to submit with your CT600.I hope this helps but let me know if you have any further questions.