Some advice for those in syndicates for tonight's big Lotto draw - put things in writing.

The second biggest Lotto prize in New Zealand history is up for grabs tonight with the jackpot reaching $38 million.

Similar big wins have historically gone to syndicates.

Lawyer Steve Cullen told Mike Hosking it's a good idea to make things very clear.

"Perhaps write a name of a syndicate on the rear of the ticket and then have a collateral contract, some sort of document that accompanies it that says these are the member of this syndicate who intend to share in the proceeds of this ticket equally."

He said even if someone's been in a syndicate arrangement for years, they still have to pay their share of the ticket this week.

"The less the intention of the parties is that you would all share whether you are there or not that's your difficulty, that's where you get into confusion and that's where people wind up being excluded from proceeds and arguments develop."

LISTEN ABOVE AS STEVE CULLEN SPEAKS WITH MIKE HOSKING