Up to half a million small and micro employers must act this year to comply with auto-enrolment or risk a fine, the Pensions Regulator (TPR) has warned.
All of these employers have received letters from the regulator alerting them when their auto-enrolment duties start, and reminding them to act.
TPR said smaller employers were more likely to "leave things to the last minute" and expected there would be late or non-compliance.
Executive director for automatic enrolment Charles Counsell said: "We are concerned that a minority of smaller employers are leaving things too late and struggling to comply on time.
"We are helping employers avoid this by alerting them in good time to their duties, and giving them the tools they need to meet them. Employers should start planning 12 months before their duties start, and make our website their first port of call."
TPR said employers should start planning by using the regulator's online duties checker which forms part of an online step by step by guide.
The regulator acknowledges not all employers have staff who need to be put into a pension scheme, but these employers remain responsible for telling workers about automatic enrolment and completing a declaration of compliance.
TPR also added employers should contact pension and software providers and business advisers "in good time".