The figure is corroborated only by secondary news reporting (Politico, TVP World, NYT, Reuters); no primary official source (Ukrainian Ministry of Finance, European Commission, IMF) publishing the exact €23 billion figure was located.
Outlets express the same shortfall in different currencies: €23 billion is the euro equivalent of the widely reported $27 billion figure (TVP World: '$27 billion, or €23.1 billion').
The figure refers specifically to the 2026 defence budget shortfall, a detail not stated in the claim itself.
Some reporting (Reuters) cites a slightly different magnitude (€27 billion / $31 billion), indicating minor variation across sources; the dominant and most consistently reported figure is €23 billion ≈ $27 billion.
Sources
SecondaryPolitico EuropeKYIV — Ukraine faces a €23 billion hole in its defense budget this year, leaving Kyiv scrambling for cash to fight Russia...
SecondaryTVP WorldUkraine says its defense ministry faces a $27 billion, or €23.1 billion, funding gap this year.
SecondaryThe New York TimesBut Ukraine now faced an unexpectedly large defense budget shortfall, President Volodymyr Zelensky told allies. To get through the year, he would need $27 billion more.
SecondaryReutersUkraine faces a pressing budget deficit for this year and next and, as the war with Russia escalates, officials say Kyiv needs an additional €27 billion ($31 billion) for defence spending in 2026.