The mobile giant stung investors with a cut in its share pay-out as it targets further investment and debt reduction.
Vodafone has swung to a €7.6bn (£6.6bn) annual loss and slashed its dividend as it focuses on investing in 5G networks and cutting debt.
The bottom line loss for the world's second biggest mobile phone operator in the year to the end of March compares to a profit of €2.8bn (£2.4bn) for the same period last time around.
Vodafone swung into the red after writing down the value of some of its assets and taking a hit on the sale of Vodafone India.
Chief executive Nick Read said the company achieved its guidance for the year in most markets but saw increased competition in Spain and Italy and headwinds in South Africa.
"These challenges weighed on our service revenue growth during the year, and together with high spectrum auction costs have reduced our financial headroom," he said.
He said the board had made the decision to cut the dividend from 40% to €0.09 per share to help reduce debt and support its goals including improving customer engagement and accelerating its digital transformation.
The company announced that it was switching on its 5G network for consumers and businesses in seven cities in the UK - Birmingham, Bristol, Cardiff, Glasgow, Manchester, Liverpool and London - on 3 July.
Vodafone reported group revenue of €43.7bn, down 6.2% on the prior year.
The figures follow its announcement on Monday night that it has sold its New Zealand mobile business for £1.7bn to a consortium of infrastructure investors.
Meanwhile, it is seeking to complete a deal later this year to buy cable networks in Germany and central Europe from Liberty Global, seeking an increased fixed-line presence to compete with Deutsche Telekom.