With Christmas orders about to flood the delivery network, published advice from the Citizens Advice Bureau, NZ Post and consumer agencies is clear on one point: a parcel that lands on your doorstep with someone else's name on it is not yours to open.

The Citizens Advice Bureau says the Postal Services Act 1998 expects anyone who receives mail by mistake to take reasonable steps to get it to the right person. It also warns that mail should only be opened if it is addressed to you by name or to "the householder".

The Act itself spells out the penalty. Section 23 makes it an offence to open a postal article that is not addressed to you if you do so "wilfully and without reasonable excuse". The maximum penalty is six months in prison or a $5000 fine. The Act defines a postal article as a letter, parcel or other item that has been posted and has not yet reached the hands of the person it was sent to.

What to do next depends on what the label says. NZ Post's help pages, updated in August, split the problem in two. If the address on the item is not yours, the company asks you to get in touch so it can arrange a pick-up. If the address is yours but the name is not, NZ Post does not treat that as a delivery error. In that case it suggests writing "Return to Sender - Not at this Address" on the item and dropping it at a PostShop or in a posting box, or contacting the sender if their details are on the packaging. For a former tenant, a landlord or property manager may have a forwarding address.

The CAB adds that if the right address is nearby you can simply take the item there yourself, and that NZ Post will collect and redeliver for people who cannot manage that.

For a parcel carried by another courier company, the common-sense course is the same: leave it sealed and contact the carrier named on the label.

If it is your own order that has gone astray, the first call is to the shop, not the courier. Consumer NZ says an online store that arranges delivery remains responsible for the goods under the Consumer Guarantees Act until they reach you. The store should do the chasing, and if the parcel cannot be found you can ask for a refund or a replacement.

Where a parcel is marked as delivered but has vanished, Consumer NZ says the outcome can turn on where it was left. A parcel placed at the front door probably meets the test of reasonable care; one left at the gate beside a main road may not.

The Government's Consumer Protection service says people who paid by credit card and cannot get anywhere with a seller should ask their bank about a chargeback, and that unresolved disputes can go to the Disputes Tribunal. The Commerce Commission does not act for individuals but takes reports about misleading conduct.

Different rules apply if you hired the courier yourself. Consumer Protection says that under the Contract and Commercial Law Act a carrier's liability is capped at $2000 for each unit of goods, usually each box, unless the contract sets different terms, and that claims must usually be lodged within 30 days.

For parcels sent by friends or family through NZ Post, the CAB says only the sender can claim compensation, because the contract is theirs.

Free advice is available from the Citizens Advice Bureau on 0800 367 222, weekdays from 9am to 4pm and Saturdays from 9.30am to 1pm. The CAB has a branch in Invercargill.