• Sage BusinessVision program doesn't stop you from voiding a paycheque, or entering a paycheque for last year
• However, doing this will affect the earnings for the current year and not last year
• T4 for last year doesn't change. The adjustment will affect the T4 for this year 

If you want the adjustment to affect last year earnings and last year T4:

1. Enter a manual journal general ledger entry for the adjustment.
2. Edit the previous year's T4 to reflect the adjustments.