If the transaction was made before 31st January 2020, it is possible that it has an old category, before Starling launched business specific categories. You’ll need to update this to a new business category before you can add any additional bookkeeping information.
VAT and tax deductibility only apply to income and expense transactions. So any transactions categorised with a Business Payment (e.g. Investment Capital, Loan Principal, Transfers), Tax Payment or Personal Payment (e.g. Dividend) category won’t have the VAT and Tax modules available in the Bookkeeping sidebar.
Any transactions categorised with a Business Payment, Tax Payment or Personal Payment will also automatically move to ‘completed’.