TNP2 entered incorrectly - new TNP or not?

If the start date is in the current contract year, you can overwrite it. If it's in an old contract year you'll need to add a new one with the appropriate date. 

great thanks

...although this depends if it's matched with the wrong value on AS...

Assuming it hasn't (and you've spotted it because of a DLOCK), fine to overwrite.

The helpdesk have advised that if the incorrect cost had been submitted in a previous collection period then a new record *is* needed, dated a day after the old one. 

Hi, Jumping on this thread! Do you need to delete the original TNP2 before adding the new TNP2 cost or will it override the old one? And do you just amend the total cost in your DAS?

Thanks in advance.

Assuming this is a learner who has already matched on DAS, then you'll definitely need an additional TNP2 or you'll get a DLOCK_07.

If you're just changing the TNP2 then this will change the total price on DAS, so yes, that will also need amending.