An extra €284m will also be given to ministerial departments
Up to 5,000 staff will be hired by the British government next year to prepare for Brexit.
The positions will be based in the Revenue and Customs (HMRC) department.
An extra stg£250m (€284m) will also be given to UK ministerial departments, as the country gears up for leaving the EU in March 2019.
The new posts and funding will be used to prepare for both a commonly-agreed departure plan and a "no deal" cliff-edge divorce.
British Prime Minister Therea May's spokesman revealed details of the plans to reporters on Wednesday.
A new Cabinet sub-committee on post-Brexit trade policy will also be set up.
It came as the spokesman was asked how Mrs May would respond to the nearly 400 amendments to the delayed EU Withdrawal Bill.
He said "we will do whatever is necessary".
Earlier, the UK Brexit Secretary David Davis told the Cabinet that 300 lawyers have been recruited to the British government's legal department in the past year.
He told colleagues: "Alongside the negotiations in Brussels, it is crucial that we are putting our own domestic preparations in place so that we are ready at the point that we leave the EU."
And Mr Davis added stg£500m (€568m) had already been committed for Brexit preparations, with the further funding earmarked for implementing border changes, trade deal agreements and converting existing EU law into UK law.