The National Party plans to make KiwiSaver compulsory for all workers, if re-elected, as part of a suite of changes that would cost more than $1 billion over four years.The party would also automatically enrol babies, pay a government contribution to those on parental leave and make employer contributions for those over the age of 65 compulsory.National leader Christopher Luxon said the party is backing New Zealanders to "build a bigger nest egg" and retire with "greater financial security".He made the announcement at the party's annual conference in Lower Hutt on Sunday.Luxon pointed to government policy announced in Budget 2025 that would gradually lift KiwiSaver contribution rates, but said National was "going further".He said everyone in work would be required to contribute to KiwiSaver, or an equivalent scheme, from 1 July 2028.The contribution amount would be set at the default rate, meaning by 2032 employers and employees must contribute 6 percent each. Workers in an alternative scheme, such as the Police Super Scheme, would be exempt."In a more uncertain world, New Zealand needs higher savings and greater financial resilience. Compulsory KiwiSaver will help deliver both," Luxon said.If elected, the party would also automatically enrol every baby born in New Zealand into KiwiSaver and contribute a $1500 payment to "kickstart their savings," Luxon said."Parents will be able to contribute further if they wish but even if they can't, their kids will be well on their way to a bigger nest egg."As well, National would provide a government contribution to parents on paid parental leave, even if they were not contributing themselves.Luxon pointed to new parents, "overwhelmingly mums", who miss out on the government's matching KiwiSaver contribution while on parental leave.That too would be made at the default rate, applied against the amount of paid parental leave a person was receiving. This would start from 1 July 2027.Luxon said many New Zealanders choose to keep working after 65, and at the moment employers were not required to make contributions after that age. National would also look to make employers maintain those contributions for employees over 65."New Zealanders who do the right thing by working hard, saving up and investing deserve a Government that backs them - not to be punished with more taxes that hit their investments and make them worse off."The policy document released as part of the announcement listed the fiscal costs.In the 2027/2028 year the changes would cost $110 million. The following year would cost $323m, then $342m, then $361m in the 2030/2031 year.Overall, that is more than $1 billion over four years.The party said it presented the most "conservative estimate" of the net cost of the policy, acknowledging there may be additional revenue from higher employer superannuation contribution tax, but had chosen not to offset the costs with that extra money.