If the qualifying earnings basis is being used, you’ll need to contribute more than the 3% total after 6 April 2019.
The minimum contributions are being introduced in three stages known as phasing.
If the qualifying earnings basis is being used, the minimum contribution until 5 April 2018 was 2% with at least 1% from the employer. Between 6 April 2018 and 5 April 2019 the minimum contribution is 5% with at least 2% from the employer, and from 6 April 2019 the minimum contribution will be 8% with at least 3% from the employer.
See The Pensions Regulator contribution levels guidance for further information.