The Canon PowerShot SX430 IS does not appear to have a standard front filter thread. As noted in community answers, the camera manual does not list any filter thread size or a compatible filter adapter, which strongly suggests screw-in filters are not directly supported.

On many PowerShot SX models, the rings around the lens are for the lens cap or trim and are not actual filter threads. That would explain why your 40.5mm UV filter will not fit.

If you want to use filters, the only possible route may be a dedicated adapter tube, but compatibility for the SX430 IS is unclear from the available information. One community answer mentions that if your lens cap/ring setup matches certain other SX models, an adapter such as the Canon FA-DC67A might be worth investigating—but this is not confirmed for the SX430 IS.

So the safest conclusion is: the SX430 IS likely does not take screw-in filters directly, and you should not buy filters based on thread size unless you first confirm a compatible adapter.