Charging interest help needed

[UKBob]

I have a client who owes us a lot of money as a stage payment on a big job. For arguments sake, lets say we are well beyond the 95% mark. Our contract states that the stage payment is due when we reach the 85% mark.

To cut a long story short, they have not paid yet. And the stage payment is more than 2 months overdue.

I thought I might go down the charging them interest route (they owe thousands).

Can I back date the interest to the middle of december, which is when the interest is due.

I have not mentioned interest in my terms and conditions, am I within my rights to announce that Im going to do so (now, for the first time) and how much notice do I need to give them.

Also, on a monthly rate, how much am I allowed to charge. is 2% a month reasonable (thats 24% a year)

Thanks in advance for your advice chaps.

[SS2.]

Its covered by the Late Payment of Commercial Debts (Interest) Act 1998 - user guide here www.payontime.co.uk/downloads/commercialdebts.pdf

Not my particular area of expertise but its something we looked at a while ago for an especially late paying customer..


>> Edited by SS2. on Wednesday 15th February 15:36