How do I change which tax head a GL account is in?

Accounts → Tax → Heads, pick the company: every income and expense GL in its trial balance under the head Saral gave it, with last year's figures beside it and the losses brought forward. Change the head where the sort is wrong — the choice is remembered. Lines flagged for review are those last year's computation did not settle. Heads never calculates a tax charge. A GL with no account code is refused ('This GL has no account code — give it one in Xero first'). Changing a head needs the Admin or Accounts role.