TL;DR The bill check no longer says that bills are missing when they're not.

A Chellow user (we'll call them Jem) said to me, 'When I run the bill check it says that some bills are missing when they aren't'.

Some background: when a bill check is run, you get back a report of the differences between the actual bill (received from the supplier) and the virtual bill (created by Chellow). You also get a list of missing bill elements, for example, say the virtual bill has the element duos-fixed-gbp, but the actual bill doesn't, then the report will say that the duos-fixed-gbp bill is missing.

So Jem was checking a single TRIAD bill that spanned an entire year. (It would have been so much easier if the supplier had just made it span March, but then we have to deal with whatever's thrown at us.) So Jem's bill only had TRIAD charges in, but all the other bills for that supply were present and correct, so the bill check should have given a clean bill of health, but in fact it was saying that some bills were missing. This kind of false positive was really annoying for Jem because it meant that they had to check for something that wasn't actually a problem.

To solve the problem we've had to make Chellow generate bills at the half-hourly level. That is to say, each half-hour has it's own virtual bill. That way we can accurately say if there are any missing bills. It was quite a big undertaking, but well worth it.