If you've made a mistake in reporting on your luxury car tax (LCT) obligations – that is, if the amount you reported on your activity statement was not correct at the time you lodged it – you can't correct it on your current activity statement. Instead you need to revise the activity statement covering the period in which the mistake was made.
If the LCT amount was correct at the time you reported it but it has since increased or decreased, you can make an adjustment on your current activity statement.
See also:
Luxury car tax mistakes must be corrected using a revised activity statement.