Britain has sought to support Ukraine during the war, providing weapons but also taking economic steps, such as cutting tariffs on all Ukrainian goods to zero.
Talks on the digital deal began in the summer and were fast-tracked with a view to supporting Ukraine's economy through the war and afterwards.
"This agreement will mean our businesses and governments can collaborate even more and ensure Ukrainians have access to essential goods and services digital trade opens up," British trade minister Kemi Badenoch said.
"This will help protect jobs, livelihoods and families now and in Ukraine's post-war future."
The deal covers areas such as streamlining digital border processes, cross-border data flows, electronic transactions and e-signatures.
Yulia Svyrydenko, Ukraine's first deputy minister and minister for trade and economy, will be in London to mark the agreement.
"The UK-UA Digital Trade Agreement has enshrined core freedoms for trade in digital goods and services," Svyrydenko said.
It is Britain's second digital trade agreement, after one with Singapore was reached earlier this year.
(Reporting by Alistair Smout; editing by William James)
