Owners of firearms and magazines that will be illegal to own from tomorrow will be able to claim compensation based on make, model and their condition.
Broad details of the buyback scheme have been released, and will be included in the legislation when it comes back to the House this afternoon.
The bill banning military style semi-automatics, magazines and parts that can be used to assemble prohibited firearms was introduced after the 15 March Christchurch terrorist attack on two mosques that left 50 dead.
Independent advisors will come up with a price list for the buyback scheme and a separate expert panel will be set up to determine fair compensation for high value firearms.
Owners can only seek compensation if the firearms were lawfully obtained and the person had the appropriate firearms licence.
New regulations for the buyback will be created; they will also provide for rights of review and appeal.
The legislation already allows for an amnesty until the end of September but will make clear that could be extended by a month to run alongside the buyback.
The government initially estimated the buyback could cost it between $100 and $200 million but as of this week did not have any firmer figures.
Police Minister Stuart Nash said police had also consulted extensively with Australian officials "to familiarise themselves with the pitfalls and legal risks encountered", after almost thirty amnesties and buyback schemes there since the 1990s.
He said a number of transitional measures were also being put in place to handle one-off questions.
"This includes weapons which were in transit from overseas when the ban took effect.
"Customs officials may deliver them to police as part of the amnesty and buyback arrangement."
Police were already collecting bank account details from people who were taking part in the gun amnesty, Mr Nash said, and were well placed to begin paying compensation once the scheme was confirmed.
"I can reassure firearms owners there will be plenty of time for them to hand over their weapons as part of the amnesty and to have their compensation processed under the buyback as well."
The bill will have its committee stages and third and final reading in Parliament today.