What is the ruling of Islamic law on paying multiple taxes, and are we sinful for doing so? And is what remains with the tax collector after payment, which the taxpayer does not reclaim, considered a bribe?

A Muslim is accountable before Allah concerning his wealth. The state is not permitted to impose taxes except to provide public services and after the state treasury has been depleted. Imposing taxes without a مقابل (counter-service/return) or when the treasury is sufficient is forbidden by Sharia, and whoever does so is threatened with not entering Paradise. It is not permissible to pay taxes in forbidden situations except under duress. It is not permissible to leave an excess amount for the tax collector out of shyness, because the wealth of a Muslim is not lawful except with his willing consent. This is not considered bribery unless it is to invalidate a right or uphold a falsehood.