Applications for the Basic Payment Scheme are now being accepted in England and Northern Ireland, but will not be open until Monday (6 March) in Wales and mid-March in Scotland.
Farmers and landowners who applied online using the Rural Payments Service in England in 2016 – covering 80% of all applications – are being emailed with all the information they need to apply online again, says the Rural Payments Agency (RPA).
Those who did not apply online, or who did not use an agent, will soon be sent a paper form and guidance notes.
But in Northern Ireland, the department of agriculture says it will no longer be automatically issuing paper application forms, but will operate online only.
Applicants with poor broadband or who are not confident with computers are advised to seek a one-to-one appointment with a single application form adviser.
It is understood the RPA plans to close its system from 4pm on 23 March to 8am on Monday 27 March for essential maintenance, so online applications should not be submitted then
Rural Payments Wales has also confirmed its online service will be unavailable on 11 and 12 March.
All applications for BPS must be lodged before midnight on 15 May.