An additional 40,000 families can now access tens of thousands of dollars in childcare subsidies, but many could be missing out because they have neglected to register with Centrelink.

Under new rules introduced on July 1, parents with one child in care and who earn more than $350,000 a year are now eligible for about $13,000 in subsidies, while those with two children under six in full-time care are eligible for $30,000. A family earning $460,000 and with two children in care can now claim $10,000 in subsidies.