Several changes in state income and sales taxes took effect July 1.

Under legislation passed by the General Assembly last session, $200 of interest income ($400 for a joint return) is no longer subject to state income tax, saving taxpayers up to $15 each (or $30 for a joint return).

Volunteers who use their own vehicles while serving a nonprofit volunteer organization that provides medical, health or nutritional care can substract 18.5 cents per mile from their total income on 1980 and 1981 returns.

Ethyl and methyl fuels generally used for farm equipment are exempt from the motor vehicle fuel tax when they are not blended with any other product, such as gasoline purchased at gas stations. Antique truck owners are exempt from the road tax on motor carriers where tax would normally apply.

New retail tax exemptions include the sales of hand tongs, patent tongs, clam or oyster rakes, dredges, handscrapes, crab pots, eel pots, fish nets and their component parts. Fuel and repair parts for commercial fishing vessels have also been exempted. Sales of wood, wood bark, wood residues or refuse-derived fuels used for heating have also been exempted, as have sales of sanitary napkins and tampons. In addition, when a restaurant charges a mandatory gratuity or tip, a group of ten persons or fewer is automatically exempt from the sales tax.