The Brexit deal has major implications for Northern Ireland.
Northern Ireland will still be part of the UK's customs territory at the end of the transition period but will also continue to follow EU customs rules.
That is likely to mean new bureaucracy for trade between Northern Ireland and the rest of the UK.
The government has promised to ensure "unfettered access" for Northern Ireland businesses to the rest of the UK but has not set out how it will do this.
The Northern Ireland Affairs Committee said its inquiry will examine the Northern Irish protocol in detail.
It is seeking written evidence that can be submitted until 1 April, on a range of questions including:
1、What customs checks, processes, declarations and infrastructure improvements will need to be implemented under the revised protocol by businesses and customs authorities in Northern Ireland and Great Britain in order to export goods from Northern Ireland to Great Britain and from Great Britain to Northern Ireland?
2、Whether the UK has sufficient customs agents, customs officials and veterinarians to facilitate the new customs arrangements?
3、 What effect the new customs arrangements will have on the volume and profitability of West-East and East-West trade between Northern Ireland and Great Britain?
4、What potential economic effects the revised protocol will have on Northern Ireland?
Chair of the Northern Ireland Affairs Committee Simon Hoare said there is an "urgent need" for clarity on customs arrangements under the protocol.
"Despite government promises of unfettered access, it now seems likely that additional paperwork will be required to move goods from Great Britain to Northern Ireland.
"Meanwhile, businesses remain in the dark about how they can get their goods to market after the transition period," he added.