Does a tapped creature deal combat damage if it was put into combat without attacking or blocking?

A creature deals combat damage only if it is a declared attacker or declared blocker during the combat phase. Simply being tapped or being 'in combat' in some informal sense is not enough — the creature must have legally attacked or legally been assigned as a blocker to participate in combat damage assignment (CR 506.4, 510.1).

Tapped creatures are specifically barred from attacking (CR 508.1a) and from blocking (CR 509.1b). So a creature that is tapped before or during the declare attackers or declare blockers step cannot be declared as an attacker or blocker, and therefore it never becomes a 'attacking creature' or 'blocking creature' in the rules sense.

If some effect puts a creature 'into combat' — such as an effect that makes a creature 'an attacking creature' without it having been declared as an attacker (like Alesha, Who Smiles at Death or 'is attacking' effects) — that creature can deal combat damage even if it is tapped, because the effect explicitly grants it attacking status. But a creature that is merely tapped and sitting on the battlefield without such an effect never deals combat damage on its own.

Example: Your opponent controls a 3/3 that becomes tapped due to a card effect during your combat phase. That creature is not a declared attacker or blocker, so it deals no combat damage that turn, regardless of being 'present' on the battlefield during combat.

Key rules: CR 508.1a (tapped creatures cannot attack), CR 509.1b (tapped creatures cannot block), CR 510.1 (only attacking and blocking creatures assign combat damage).