You will need to work out credit adjustments that are added in with GST on purchases and expenses.
Bad debts written off
If you make and account for a supply and later write off all or part of the consideration as a bad debt, you may make a credit adjustment in the period you write it off.
Include 3/23 of the amount you have written off in the credit adjustments box of your GST return.
You do not need to send in any documents supporting the write-off, but you do need to keep a record of the steps you took to recover the debt.
If the bad debt was for a supply when GST was not charged on the full price (such as the fifth week of a hotel stay, or a hire purchase sale), work out your credit adjustment using the calculation:
bad debt written off / total consideration x GST included in consideration = GST adjustment.
Using the payments basis
If you use the payments basis and do not receive payment for a debt you write off, you cannot claim a deduction as you have not included the GST on any return. For hire purchase agreements and door-to-door sales, you may make an adjustment if you use the payments basis.
GST paid to the New Zealand Customs Service
You should not include GST paid to Customs on imported goods in your purchases and expenses. This should go in the credit adjustments box.
When you can claim GST paid to Customs depends on your accounting basis.
Using the invoice basis
Claim the GST in the period you get the invoice or make the payment, whichever is earlier.
Using the payments or hybrid basis
Claim the GST in the period you make the payment.