As is stands, parents are able to claim their children as dependents on their tax returns, which lowers their overall tax liability and in effect means that the parents either pay less in taxes or receive a higher return at the end of each year.
Until they reach the age at which they can work, children are a drain on society. They receive public schooling and receive the same benefit from public services that adults do, yet they contribute nothing in return. At the point that they reach maturity and are gainfully employed and paying taxes, they become a functioning member of society.
If a parent decides to have a child, they are making a conscious decision to produce another human being. They could choose to get a sterilization surgery, use birth control, or abort the pregnancy (assuming they don’t live in a backwards state that’s banned it). Yet even if they decide to have 15 children, the rest of society has to foot the bill for their poor decisions until the child reaches adulthood.
By increasing taxes on parents instead of reducing them, you not only incentivize safe sex and abortion, but you shift the burden of raising a child solely to the individuals who are responsible for the fact that that child exists.
I am a strong advocate for social programs: Single-payer healthcare, welfare programs, low-income housing, etc, but for adults who in turn contribute what they can. A child should only be supported by the individuals who created it.
Individuals choosing not to have kids should pay an extra tax that should go to the ones having children.
Choosing not to have children is a perfecly acceptable individual choice, but the consequence is that you become a net negative for the economy.
Taking on the burden of child-raising is an essential task that is net positive for the economy, which has been way underappreciated for too long.
If people don’t reproduce enough, we aren’t going to have enough workers. Fortunately though, there’s always a steady flow of immigrants to solve that problem in wealthy countries. After a few hundred years, many societies might look very African/Arab/Asian. If you want to further speed up that process, you could start taxing reproduction too.
Your taxes should go up each decade you age without having children. If you have a kid some of that could be refunded as an incentive.