"Fast track for those who left in the last 12 months; you could be serving again within 4 weeks."
Express.co.uk has asked the Ministry of Defence how long it would take for someone to rejoin who left more than a year ago.
It comes as the Army has been helping in the response to the coronavirus outbreak.
Military personnel have been working 15-hours shifts to transform the ExCel centre in London into the new 4000-bed NHS Nightingale Hospital.
Up to 200 personnel have been assisting contractors and NHS staff with the hospital's construction.
Harry reached the rank of Captain during his 10 years in the Army and also undertook two tours of Afghanistan.
He left the military in June 2016 to start a "new chapter".
At the time, Harry said: "After a decade of service, moving on from the army has been a really tough decision.
"I consider myself incredibly lucky to have had the chance to do some very challenging jobs and have met many fantastic people in the process.
"From learning the hard way to stay onside with my Colour Sergeant at Sandhurst, to the incredible people I served with during two tours in Afghanistan — the experiences I have had over the last ten years will stay with me for the rest of my life. For that I will always be hugely grateful."
Harry is currently based in the US with Meghan Markle and their son Archie.
The Duke and Duchess of Sussex officially quit as working royals on March 31.
In a goodbye message on their Sussex Royal Instagram account, they said: "As we can all feel, the world at this moment seems extraordinarily fragile.
"Yet we are confident that every human being has the potential and opportunity to make a difference—as seen now across the globe, in our families, our communities and those on the front line—together we can lift each other up to realise the fullness of that promise.
"What's most important right now is the health and wellbeing of everyone across the globe and finding solutions for the many issues that have presented themselves as a result of this pandemic.
"As we all find the part we are to play in this global shift and changing of habits, we are focusing this new chapter to understand how we can best contribute.
"While you may not see us here, the work continues.
"Thank you to this community - for the support, the inspiration and the shared commitment to the good in the world.
"We look forward to reconnecting with you soon. You've been great!
"Until then, please take good care of yourselves, and of one another."
Harry, who served in the Army for 10 years, could return as they are calling for people to rejoin in the battle against Covid-19. The Army's website says: "We value your previous service, and if you're thinking of coming back, there's a job waiting for you.
"If you have served in the Regular Army, you can return to full time service even if you left under the Armed Forces Redundancy Scheme.
"There are also opportunities for personnel from the other services to join the Army."
An Army Twitter account added: "People who left in the last 12 months could return within four weeks but it could take longer for those who left over a year ago.
"Want to rejoin the @BritishArmy? The Army is committed to maximising its size during the outbreak of #coronavirus.