The European Commission has produced a map of where it expects the UK to apply internal customs checks under Boris Johnson's Brexit withdrawal agreement.
The prime minister has repeatedly denied that his deal includes customs checks between Great Britain and Northern Ireland, but his claim is contradicted by the contents of the treaty.
Sabine Weyand, the EU director general for trade, said that "now that the withdrawal agreement has been signed", Brussels would be publishing a guide to the deal, "including how the protocol on Northern Ireland will work".
Two slides in the guide include maps illustrating the checks and controls on goods going in both directions between Great Britain and Northern Ireland.
The checks are most substantial in the Northern Ireland-bound direction, with exit formalities for the UK to determine at British ports such as Liverpool.
Upon arrival in Northern Ireland, the UK will have to apply relevant EU rules and carry out any required checks under the Brussels rulebook.
The guide notes that EU institutions will have the same oversight as today, with the European Court of Justice as the final arbiter. EU representatives will also have the right to be present at the internal checkpoints and monitor the activity.
Live animals, animal products, and plants will have to face regulatory checks, while industrial products will face "risk-based" spot checks when passing between the two parts of the UK.
Some tariffs will have to be paid if goods are considered "at risk of entering the EU". EU legislation on VAT and excise will apply.
Checks will also apply when moving from Northern Ireland to Great Britain: anyone transporting goods between these parts of the UK will have to fill in an EU export pre-departure declaration and comply with EU export formalities.
Upon arrival in Great Britain, the goods will face UK entry formalities to make sure they comply with WTO and trade agreement rules. The Treasury has previously said that food and security checks would be required in order to avoid any goods "having circumvented UK tariff and regulatory controls".
The prime minister has repeatedly made false claims about the withdrawal agreement. Asked by a Northern Irish exporter at the end of last year whether they would have to fill in extra forms to export to Great Britain, he said "absolutely not.”
Mr Johnson said that any export declarations should be sent to him personally “and I will direct them to throw that form in the bin”.
The prime minister made repeated false claims throughout the election campaign that checks were not part of the withdrawal agreement, suggesting that he either did not understand the treaty, or that he was lying.
Asked whether he stood by his assertion that there would be no checks on goods travelling between Northern Ireland and the British mainland, a Downing Street spokesman said: “The prime minister has answered this question many times in the house and has re-emphasised that there will be no checks.”