Careful economics and careful carpentry have one thing in common. Building things level is not easy when the floor is a bit crooked. We need to be a bit careful about retailer demands for level playing fields around tax on imports.

As more of us buy from overseas, New Zealand retailers are quick to point to uneven playing fields favouring foreign suppliers. Under the de minimis threshold, imported goods are not taxed unless the amount collected would exceed $60.

All current methods of collecting GST at the border add substantial hassles for consumers buying from abroad, make life difficult for foreign shippers serving Kiwi customers, or wind up costing IRD more than the value of the tax collected.

If there were any simple way of applying GST at the border on low-value imported goods, Inland Revenue would already have done it – both to increase revenue and to avoid having to rely on less efficient taxes. Both National and Labour have wanted to find solutions. It is possible IRD will find one, and international agreements to make it easier are imaginable. But it is not ready yet.

Without good ways of handling tax at the border, trying to level the levelling the pitch on GST risks skewing it in other ways.

While large international shippers like Amazon might jump through new hoops to be able to serve New Zealand customers, it is unlikely that smaller retailers would. Making online shopping harder by holding goods at the border until customers log in to a Customs website to make a GST payment creates distortions too. Either way, New Zealand consumers would risk losing access to the broader range of goods that international online shopping provides.

Some of those arguing for GST at the border might view those hassles as a feature, rather than as a bug.

And there is one other worrying bit. While New Zealand’s size and distance have their advantages in a maddening world, we wind up with less competition in some markets than larger places enjoy. Foreign online retailers add competitive pressure that can even benefit consumers who never shop online.

The uneven playing field on GST might then be tilting things, just a bit, against another uneven part of the pitch. The shim that makes a table unbalanced on an even floor might be just the thing to prevent wobbles in an older house.