Almost one in six adult care providers have made mistakes in applying to register with the Care Quality Commission, costing the regulator in staff time and morale.
Of 8,954 applications since April, 1,343 contained errors and needed to be returned to providers for clarification.
Unison has already warned that the registration process is loading pressure onto CQC staff, in part because application forms are having to be returned and redone. It said this had contributed to low levels of morale at the regulator, identified in its annual staff survey.
The CQC must register all 24,000 adult care providers by 1 October. Applications are being staggered with providers allotted a 28-day window in which to complete the process. The first calls to apply were issued in April this year.
Provider bodies blamed the CQC for the errors saying they sprung from confusion over which "regulated activities" providers should categorise themselves under. These include personal care, which applies to domiciliary care agencies, nursing care (nursing agencies) or accommodation with nursing or personal care (nursing or residential homes).
Frank Ursell, chief executive of the Registered Nursing Home Association, said some nursing homes had wrongly applied under either nursing care or personal care, but said this could have been avoided had the CQC indicated these referred to nursing and domiciliary care agencies respectively.
"They got what they deserved," he said. "A lot of the mistakes were obvious and I tried to advise them of that before the process."
Colin Angel, head of policy at the United Kingdom Homecare Association, said: "UKHCA is disappointed with a lack of consistency from CQC over how the new regulated activities have been interpreted, making it difficult for providers to make correct applications."
However, the CQC said this was not a major cause of errors, which were mostly mistakes in company names, such as leaving suffixes like "ltd" off.
A spokesperson added: "We took feedback from a wide range of people and organiations and tested all of the application forms with our Provider Advisory Group, which is made up of all the main trade associations in adult social care."