How does “Heads, losses and the computation” work on the Tax page?

Heads is the sort: each GL in each head, last year's figure beside this year's, the lines to review flagged, the head changeable by a person and remembered. Losses is the ledger: brought forward by head and year as the computations on the Signed Accounts shelf state them, this year's movement from the computation, how each head's loss can be used and how soon, a warning where one may lapse, and the change history; the company's tax facts — type, close company, close investment-holding, associated companies — are set here and read everywhere else. Computation lays the same figures out as a statement, group-wide with a total or one company with its loss movements and the few inputs the books cannot give (capital allowances, gains), and Position is the headline of it. One engine runs all of them, with or without group relief, for the year or the year to date. Where: Tax (/accounts/tax-planning).