We never charge the interest we're entitled to
Late payment carries a statutory rate and a fixed recovery sum, and almost nobody calculates either.
What's happening?
Where a contract doesn't provide its own remedy for late payment, legislation implies one: interest at a statutory rate, plus a fixed sum per invoice towards recovery costs. Very little of it ever gets invoiced - partly relationship nerves, partly because nobody has worked out what it adds up to - so the entitlement stays theoretical and paying late stays free.
Calculating it changes behaviour twice. On the account: across a year of late certificates the number is rarely trivial, and stating it - even once, even unclaimed - reprices the other side's habit. Internally: the calculation doubles as the audit trail of who actually pays on time, which sharpens both the chasing and the next tender's view of that customer. Whether to claim it is a commercial judgement, made case by case; knowing the number costs a spreadsheet.
The solution
The cost of paying you late, calculated and on the table.
If you would rather it were done for you, Payment Application Assembly & Issuance is the service that does it.