Havan (Sanskrit English)

ओं यदस्य कर्मणोऽत्यरीरिचं
यद्वा न्यूनमीहाकरम्।
अग्निष्टत् स्विष्टकृद् विद्यात्
सर्वं स्विष्टं सुहुतं करोतु मे।
अग्नये स्विष्टकृते सहुतहुते
सर्वप्रायश्चित्ताहुतीनां कामानां
समर्धयित्रे सर्वान्नः कामान्त्समर्द्धय स्वाहा।
इदमग्नये स्विष्टकृते इदन्न मम।

Om yadasya karmaṇo‘tya-ree-richam
yadvaa nyoonam-ihaa-karam.
Agniṣh-ṭat sviṣhṭa-kṛid vidyaat sarvam
sviṣhṭam suhutam karotu me.
Agnaye sviṣhṭa-kṛite suhuta-hute
sarva-praayash-chitta-ahuteenaam
kaamaanaam samar-dha-yitre
sarvaanah kaamaant-samardhayah svaahaa.
Idam-agnaye sviṣhṭa-kṛite, idanna mama.¹

yat-asya whatever of this karmanah performance that ati-aree-richam has been done outside of the norm (incorrectly or improperly), yat-vaa whatever is nyoonam less than ihakaram as required. O agnih all-knowing svishtakrit fulfiller of desires, you vidyaat sarvam know that all is svishtham with best efforts and intent for suhutam karotu me my success and bliss. O agnaye svishtakrite God who grants success and who suhutahute sarva-praayashchit-aahuteenaam accepts noble (acts of) sacrifice and understands our kamaanaam wishes and desires, samardhayitre sarvaan kaamaan samardhaya may all the noble desires and wishes of the performer (of this sacrifice) be fulfilled. 
Idam agnaye This dedication is for the all-knowing svishtakrite fulfiller of our desires. idam this is na not mama for self.

यत् whatever अस्य of this कर्मणः performance/action अति very, too अरीरिचम् away, outside of precept/norm/verse यत् whatever वा or न्यूनम् less इह in this अकरम् is required, also refers to the concept of the first principle, ie letter A without which no other sound is expressed अग्नि all-knowing तत् the/that स्विष्टकृत् fulfiller of noble wishes विद्यात् knows/knower सर्वं all स्विष्टं स्विष्टम् good wishes also, best efforts सुहुतम् success करोतु may do मे my अग्नये all-knowing स्विष्टकृते for Him who makes this sacrifice successful सहुतहुते together with सर्वप्रायश्चित्ताहुतीनाम् of all noble offerings कामानाम् wishes/desires समर्धयित्रे for the performer सर्वान्नः all our (सर्वान  नः) कामान् wishes समर्द्धय pray/fulfil स्वाहा offer, homage इदमग्नये this fire procedure/process स्विष्टकृते for Him who makes this sacrifice successful इदम् this नः not मम mine, my

ओं प्रजापतये स्वाहा।
इदं प्रजापतये इदन्न मम।

Om (prajaapataye) svaahaa. 
Idam prajaapataye, idanna mama.³

प्रजापतये nourisher, father, provider स्वाहा homage इदम् this प्रजापतये provider इदम् this नः not मम mine, my

ओं भूर्भुवः स्वः। तत्सवितुर्वरेण्यं भर्गो देवस्य धीमहि। धियो यो नः प्रचोदयात् स्वाहा॥

Om bhoor-bhuvaḥ-svaḥ. Tat savitur vareṇyam bhargo devasya dheemahi. Dhiyo yo nah pracho-dayaat svaahaa.

Then, three final offerings are made  with:
ओं सर्वं वै पूर्णं स्वाहा।

Om sarvam vai pooram svaahaa