The organisation is set to deliver on the public promise it made in late July, when it signalled its "armed struggle" was over and said it would put its faith in politics rather than violence.
The move is set to be widely welcomed, though the scepticism surrounding the republican movement means nothing will be taken for granted and much verification will follow.
Most immediately the IRA announcement is to be confirmed by General John de Chastelain, chairman of an international commission on decommissioning, who is expected to say this afternoon that he has witnessed the republican armoury being put beyond use. Further evidence of this is to be given by two clergymen, a Protestant minister and a Catholic priest, who have been nominated as witnesses to the acts of decommissioning.
The priest is Fr Alex Reid of Clonard Monastery in west Belfast, who is close to the Sinn Fein president Gerry Adams. The Protestant witness is the Rev Harold Good, a senior Methodist who has been involved in reconciliation and cross-community work.
If all goes according to plan, it will be argued that a significant corner has been turned in the Irish peace process, and that the departure of the IRA as an active force will give the flagging process a huge boost. The next step will be a period of some months when republicans will be closely scrutinised by the security forces and the Independent Monitoring Commission to ensure IRA activity has indeed ceased.
British and Irish ministers have already confirmed that there has been no IRA activity since the organisation's statement of 28 July. The two governments are reasonably confident the IRA will keep its word, given that it will be under the closest scrutiny locally and internationally.
No immediate welcome is expected from the Rev Ian Paisley, whose Democratic Unionist Party dominates Unionist politics. He has the crucial say on whether, and when, a new cross-party administration might be formed in Belfast.
He has already complained that the IRA has refused to comply with his demand that photographs should be taken of the decommissioning, and has argued that events such as last year's Northern Bank robbery show that republicans cannot be trusted.
The authorities hope that the anticipated tough initial reaction will gradually soften with security forces indicating that the IRA has indeed become inert. Both London and Dublin hope that high-level political talks will eventually be held, but few believe this is likely to happen before next year.
The IRA and Sinn Fein have been paving the way for decommissioning with great care, holding many meetings to reassure their grassroots that guns are no longer necessary and that in their place Sinn Fein wields considerable, and growing, political clout.
Gerry Adams, who spoke at a republican rally in Dublin on Saturday, predicted political conditions "will dramatically change" following the IRA move. Sinn Fein's chief negotiator Martin McGuinness will fly to Washington tomorrow.Reuse content