Yellow wrote:

There must surely be a method in place whereby employers are told to
stop collecting when the debt has been paid otherwise everyone will be
over paying?

Is the answer therefore to pay off it all save for the last three or
four months worth of payments and then the system that already exists
will notice the debt is complete and will send a cancel request. The
fact you have paid a lump sum would then be neither here nor there.

The Student Loan Company don't even know what repayments they have received
until they receive their copy of the details HMRC get from the end of year
payroll returns. It generally takes HMRC until about August to process
these, then they can pass them to SLC and SLC can do their processing.

I would suggest that anyone who has a Student Loan keeps very careful
records of what they have paid, and how much interest should have been
charged on the remaining about, because the way the system is set up, the
Student Loan Company has no more than a random chance of getting this
right.