The IRS has announced that its Offshore Voluntary Disclosure Program (OVDP) will end on 28 September 2018.
US citizens are subject to US tax on worldwide income even if they are not resident in the US.
A failure to comply may result in civil and criminal penalties being imposed.
The OVDP enables US ex-pats to voluntarily resolve past non-compliance with reduced penalties and interest for voluntary disclosure.
A voluntary disclosure will not automatically guarantee immunity from prosecution - however, in practice a voluntary disclosure usually results in the IRS recommending no prosecution.