Experts hired by the coalition to check its election policy costings say the figures are based on "reasonable assumptions".
Former senior public servant Peter Shergold, former Queensland auditor-general Len Scanlan and co-founder of Access Economics Geoff Carmody on Thursday handed over their report on coalition costings to shadow treasurer Joe Hockey.
Mr Hockey is due to release the costings later on Thursday.
Speaking at a photo opportunity to release the panel's report, Dr Shergold apologised for having taken eight months to complete the work.
"But we were absolutely determined we were not going to sign off until we'd seen every single costed policy," Dr Shergold said.
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"I think it's been a very good process."
Mr Carmody said the process, which involved detailed work by the Parliamentary Budget Office, had been "proper and thorough".
Dr Scanlan said it had been a "robust process".
The endorsement letter read: "Based on careful examination of the information provided and explanations given, we have now completed our review."
"We are of the opinion the final policy costings provided by the coalition in the attached papers are based on reasonable assumptions and calculations and as such represent a fair estimate of the net financial impact of these policies on the federal budget on both the budget balance on a cash and fiscal basis and commonwealth debt over the period 2013/14 right through until 2016/17."
"So we've signed off on that basis," Dr Scanlan said.
