1099 applicable voucher not picked up on copy B

Good Morning,

We ran into an issue where we have a few voucher lines which were withholding applicable, they were 2013 invoices, entered in 2013 but were not paid until 2014. These vouchers didn't get picked up for the copy B because the declaration date was a 2013 date, we had to make an adjustment and update the declaration date which then made them available to be picked up to be reported in 2014.

We were wondering why the declaration date did not pull from the paid date in 2014 and thus show on the copy B? How is the declaration date defined for the 1099 transactions?