Loan offset

Plan sponsor has opted for the loan to be offset, the plan is terminating any idea how the loan offset can be dealt with since some of the participants have taken the distribution and the loan is still outstanding. 

What do you mean the sponsor has "opted" for a loan offset? The plan has a written loan policy, the sponsor needs to follow those procedures which will dictate when a default and offset will occur.

A distribution upon plan termination would apply to a participant's entire account, including their outstanding loan. So the loan offset should just be a matter of reporting correctly. If the participant elected a cash distribution (not a rollover) don't forget to take the amount of the outstanding loan into account when calculating the amount of withholding.

see this related thread with similar question earlier today.

If the participant has already taken the cash distribution and if the loan is outstanding and wishes to offset, I assume this will fall into QPLO correct? and I believe we will require to code the loan correctly on their 1099 and taxes are deducted correctly for the loan correct? 

The loan probably should have been offset at the time of the cash distribution but yes it sounds like a QPLO and you just need the correct accounting entries and 1099-R.