Est. Corporation Tax in Custom Report

I have a custom report partially set up with the intention of keeping a real-time record of tax liability (CT + VAT + PAYE). The VAT aspect is straightforward (Net VAT Position: 2200+2201), but the CT seems more difficult, and I haven’t yet read up to know where to start with the PAYE.

For the CT, I’d like to use the “Est. Corporation Tax” figure from the built-in Tax Summary report, but I can’t find a way to do that in a custom report. Is this a feature that could be added, or could you provide the formula that’s used in the background to get the “Est. Corporation Tax” figure so I could repeat it in my custom report?