What systems will be affected?

Various types of financial systems will be affected, including:

1. Sales and ledger systems that calculate VAT from a base price will need the rate changed. Various transition issues will need to be addressed. See notes in previous post.
2. Sales and purchasing systems that have VAT-inclusive prices will need to be adjusted
3. Quotation and purchasing systems may need the Ts&Cs adjusted
4. Employee expense systems that back-calculate VAT from VAT-inclusive figures will need to handle expenses incurred either side of 1 December
5. Forecasting systems will need to apply different rates of VAT at different times

The systems you use will likely include a mixture of packaged software, spreadsheets and other internally-developed systems. The changes needed for each one will need to be evaluated, and actioned swiftly.