Present perfect vs past simple - for, since, ago

This lesson explains when to use the present perfect and the past simple, and how the time expressions for, since and ago affect the choice of tense. You'll learn the structures and common patterns used in English to talk about finished actions, ongoing situations, and durations.

• Present perfect: have/has + past participle — used for actions connected to the present or durations that continue to now.
• Past simple: past form of the verb — used for actions completed at a specific time in the past.
• 'For' + duration, 'since' + point in time, 'ago' + time before now — each pairs with a tense in typical contexts.

Remember the basic decision process:

• If the action or situation continues to the present → use present perfect + for/since (e.g. have worked for five years; have worked since 2018).
• If the action is finished and refers to a specific past time → use past simple + ago or other past time expressions (e.g. started five years ago; finished yesterday).
• Use 'for' with a duration (for two months), 'since' with a starting point (since March), and 'ago' to locate a past time measured from now (three days ago).

Think: continuing → present perfect (for/since). Finished → past simple (ago, yesterday, in 2010).

Watch for these universal errors students often make:

• Using present perfect with a finished past time (e.g., 'I have finished yesterday' — incorrect).
• Using 'since' with a duration instead of a starting point (e.g., 'since two years' — incorrect).
• Using 'for' with a point in time (should be a duration).
• Using 'ago' with present perfect (e.g., 'I have lived here two years ago' — incorrect).
• Forgetting the auxiliary 'have/has' in present perfect, or using incorrect past participle forms.

Check the time expression first (for/since/ago) — it often tells you which tense to use.