Finnish present perfect

The Finnish present perfect is constructed along the following lines:

pronoun + present of olla + past active participle (-nut/-neet)

Notice how in English the auxiliary verb is have but in Finnish it is olla. Estonian is the same in that its aux. v. is also olla.

FOR: Minä olen kirjoittanut hänelle.
COL: Mä oon kirjoittanut sille.
E: Ma olen kirjatanud talle.
I have written to him/her.

Remember that in Finnish there is the difference between formal and colloquial registers visible above in both the forms of the pronouns and the aux. v. and below in the pronoun.

FOR:  Hän on tullut takaisin.

COL: Se on tullut takaisin.

E: Ta on tulnud tagasi.

S/he has returned.

An interesting thing about Finnish is the presence of a plural form of the past active participle with the ending -neet. This is something that Estonian does not have.

Compare the following:

Polite singular: Te olette tullut takaisin.

You (sg.) have come back.

Plural: Te olette tulleet takaisin.

Ye/Y'all have come back.

In Estonian this is simply:

Te olete tulnud tagasi.

Context will tell us if it is plural or singular polite.

F: Mä oon aina unelmoinut elämästä teatterissa.
E: Ma olen alati unistanud elust teatris.
I have always dreamt of a life in (the) theatre.

F: Oletteko te asuneet Helsingissä kauan?
E: Kas te olete kaua Helsingis elanud?
Have you lived in Helsinki for long?

Things get a little complicated in the 1st person plural (me) because of the use in colloquial Finnish of the impersonal (passive/ indefinite).

Here we use:
1) The indefinite form of the verb olla.
2) The past passive participle (not the past active participle as above!)

COL: Me ollaan jo puhuttu tästä.
FOR: Me olemme jo puhuneet tästä.
E: Me oleme juba rääkinud sellest.
We have already talked about this.

COL: Me ollaan juotu kaikki oluet.
FOR: Me olemme juoneet kaikki oluet.
E: Me oleme kõik õlled ära joonud.
We have drunk all the beer.

Present perfect of the verb ostaa 'buy, purchase'. In bold is the colloquial form and in brackets the formal or polite form(s).

1sg: mä oon ostanut (minä olen ostanut)
2sg: sä oot ostanut (sinä olet ostanut / te olette ostanut)
3sg: se on ostanut (hän on ostanut)

1pl: me ollaan ostettu (me olemme ostaneet)
2pl: te olette ostaneet
3pl: ne on ostanut (he ovat ostaneet)

Thanks to ainurakne on Unilang.org for corrections!