Grand Chief David Harper, who represents Manitoba's northern reserves, says he hasn't done anything wrong.
Harper says he hasn't been suspended and is working to clear his name.
He says he's requested all the transactions in question and is taking the coming week to get to the bottom of the charges.
Harper acknowledges he does travel with his girlfriend, but says any extra costs are deducted from his paycheque.
He says the guitars that were purchased were bought as gifts for a Christmas party and not for his own personal use.
The grand chief said he sometimes travels with other staff at Manitoba Keeewatinowi Okimakanak, who may have racked up some of the charges.
The organization, which represents some of the province's poorest reserves, is undergoing an audit. Harper said he's resisting calls to step down voluntarily and the organization has no mechanism to force him to leave.
Although chiefs could put forward a vote of non-confidence motion in his leadership, Harper said that hasn't happened.
"I want to make sure my name is cleared," he said Thursday. "All my personal transactions that were made public, I want to clear those. I told the chiefs I'll be making my report to the executive within a week."
Harper has been grand chief since 2009 and is host of the Assembly of Manitoba Chiefs national chief election in December.
He rose to national prominence during the outbreak of H1N1 when he denounced the federal government for sending body bags to flu-stricken reserves rather than resources to fight the illness.