In most instances, it will be possible to submit returns and information in the usual way using either HMRC or commercial software, but there may be delays in receiving an electronic acknowledgement. In some cases, acknowledgements will not be sent until early on the morning of Monday 7 April.

The online agent authorisation service will be affected, along with self assessment, VAT online, machine games duty, charities, construction industry scheme, corporation tax, pension schemes and stamp taxes.  

The PAYE service will undergo a scheduled upgrade between Friday evening and Sunday morning. During this period it will still be possible to submit returns using Basic PAYE Tools or commercial software for PAYE end of year, in-year, expenses and benefits and Real Time Information (RTI). However there will be a delay in receiving online acknowledgement between 22:00 on Saturday 5 April and 03:00 on Sunday 6 April, and HMRC is advising users not to attempt to resend submissions.

Details of the scheduled upgrades to online services are shown on HMRC’s website and regularly updated. The information is here: http://customs.hmrc.gov.uk/channelsPortalWebApp/channelsPortalWebApp.portal?_nfpb=true&_pageLabel=pageNoNavigation_ShowContent&id=HMCE_MIG_009921&propertyType=document#toc