I think I have the new VAT rate change worked out...
The logic is simple, and always has been simple.
The VAT rate applicable is the one at the tax point.
Suppliers can, optionally, bill in advance and split on the date of VAT change, but they do not have to, and it is the suppliers choice.
So, for 1st January invoices that are for services for all of January, the VAT rate is 17.5%. Simples!
Unfortunately the Finance Act adds some extra confusion. In almost all cases that does not cause us a problem, but I think it does for a few of the invoices.
Basically, if the customer is a connected party (i.e. family member, a related company, etc), and they cannot reclaim VAT, then they have to be charged a supplementary 2.5% VAT on the period after the VAT change. This also applies in some other cases such as invoices over £100,000, but that is not an issue.
So, for the most part the invoices are as normal, and no problem.
However, I expect I'll have to charge my parents a supplementary 2.5% VAT from 4th January until the next full moon (they are invoiced every full moon). I probably should try and work out if employees count as "connected parties" too. That is assuming being parent of director of the company makes them "connected" - I'll have to read another Act to check that, or maybe I'll just email HMRC...
Why the hell make is so damn complicated? Arrrrg!