A guide for people making the decision for the first time.
Most people meet this once and never think about it again, which is exactly why it is worth reading up on.
What to check first
The figures move about, but the direction has been the same for three years. The exceptions matter more than the rule, and there are three of them.
The exceptions
Nobody is required to explain this to you, which is half the problem. There is a deadline involved, and missing it costs more than the difference.
What actually changed
The figures move about, but the direction has been the same for three years. Most of the confusion comes from two terms that sound alike and mean different things.
It rewards a little attention now and punishes leaving it to next year.