Postal staff around the UK have told the BBC that managers instructed them to remove or stash first-class letters so rounds appeared completed, a practice they say has helped mask missed delivery targets.
The claims come from ten postal workers who spoke anonymously to BBC Your Voice.
They described mail being put on trolleys or moved out of sight and returned the next day when inspections or senior managers visited.
Workers say the pressure to prioritise parcels, cuts to overtime and no increase in staffing make it hard to deliver both parcels and letters on the same shift.
They added that hiding post is used to avoid showing undelivered first-class mail during checks.
Royal Mail is due to face questions from MPs about widespread postal delays this week.
The company said it takes allegations of hidden mail seriously and that it will investigate specific cases raised.
Performance figures show why scrutiny has intensified.
In 2024-25 Royal Mail delivered only 77% of first-class letters on time and 92.5% of second-class items, missing statutory targets of 93% and 98.5% respectively.
Ofcom has fined the company about £37m in recent years and warned fines could continue without improvement.
The Communication Workers’ Union blamed poor pay, difficult working conditions and a strained managerial culture for recruitment problems and low morale among staff.
Postal workers told the BBC many feel unable to finish their workload and that sickness and stress are rising.
Royal Mail is also rolling out a new delivery model that reduces how often second-class mail is taken out.
The company says pilot areas have seen improvements — with the share of addresses receiving mail each day rising from roughly 92% to 97% — and that the new approach will make services more reliable and sustainable.
But some staff in pilot zones told the BBC the changes have made matters worse for postal workers and customers, adding that rounds are increasingly impossible to complete and morale is at an all-time low.
Customers say the delays are having real consequences.
One pensioner now travels every Saturday to his local delivery office to collect letters because they would otherwise sit undelivered, sometimes including important NHS correspondence.
MPs are set to press Royal Mail leaders on these issues, seeking answers on delivery failures, the alleged practice of concealing mail, and how the company plans to restore reliable letter service across the country.
