The Swiss authorities online
Under normal circumstances, you pay cantonal and communal taxes in instalments. These are spread out over the year and cover the amount of tax you are expected to owe in that tax year. The number of instalments differs from canton to canton. After the final assessment is issued, you receive a final statement showing the actual amount due set against the amount you have paid in instalments. In some cantons you can pay in monthly instalments or make a single payment (in some cases with a small discount).
If you do not pay your tax instalments on time you will be charged default interest.
You can also ask to pay in instalments (either with or without an agreement on extra time to pay) if you find it difficult to pay your taxes otherwise. Contact the tax administration in your canton of residence in order to set up a payment agreement.
If you do not pay any of your taxes within a certain period, the tax office will begin debt collection proceedings against you.