Standard & Poors has reaffirmed the AA ratings of KiwiBank and New Zealand Post.
The credit rating agency says both companies have stable outlooks, but says there is likely to be future pressure on NZ Post's rating as KiwiBank's liability grows.
NZ Post is the owner of KiwiBank.
Credit analyst Anna Hughes says New Zealand Post's rating is underpinned by the strength of the company's market position, as well as its supportive relationship with the Government and solid cash performance.
Ms Hughes says KiwiBank has mitigated the startup risks it faced in 2001 and benefits from having a good management team, retail-funding position and satisfactory capitalisation.
However, she says its credit quality remains weaker than New Zealand Post's traditional business.