Duplicate (or too few) employment records held by HMRC:
If the employment records held by HMRC contain duplicate employments,
and therefore do not match the employment records held by the
employer, it's likely that we will be expecting the employer to pay
more than is actually due. We have published guidance about avoiding
the creation of duplicate employments to software developers and in
our pilot employer updates.
This of course, is fine up to a point, but neither employers nor software providers or payroll bureaux are creating duplicate records on purpose to cause problems.
I'm hoping that HMRC will make an effort to find out what the source of the issues is and offer some help in sorting it out. I hope they won't be looking for a way to try and complain they are being sent bad data (even if strictly speaking they are) - because a lot of people have spent a huge amount of time and cash trying to comply with their requirements.
Not many payroll people are also systems experts so some of these issues are not immediately transparent to them - I suspect the same is true for many in HMRC - but it's no good HMRC just saying "you're wrong" if a new system seems to be doing unexpected things. Clearly, as I alluded to in my first posting, if you are suddenly "underpaying" by a significant amount that is worthy of further investigation and not just a demand to "pay up"
Fingers crossed. Like all postings here - this is a purely personal view.