No question exists that the Parson's Prologue and Tale and the Retraction belong together. They are firmly linked by the speaker and the repeated themes: "wey" or pilgrimage is the subject of both the Prologue and the Tale; penitence joins the Parson's Tale to the retraction.
     Nor is there any doubt that the fragment containing these pieces was intended as the final section of the Tales: a position it holds in all mss. The length, prose form, dullness, and somber tone of the Tale, leading to the statment of authorial remorse and the retraction of what readers through the centuries have found to be Chaucer's best poetry, pose serious questions regarding the relation of the Fragment to the preceding tales, its function in the Tales and the unity of the whole Canterbury Tales.
     Some critics claim that the Parson's Tale in only accidentally the last tale in an unfinished work. Why is this not possible to hold seriously? [Repeated stress in the Prologue that it is last and the seemingly deliberate use of verbal echoes of the other tales and of literary motifs.] Balwin showed the unity of the CT by noting that many moral statements in the Parson's Tale can be applied to individual pilgrims and their characters. CT is unified by the image of the pilgrimage first as it refers to the fictional journey to Canterbury and, secondly, in Fragment X as it refers to the religious metaphor for human life.
     Still critics debate how to describe the relation of the Parson's Tale to preceding tales. Some relate specific passages to specific pilgrims. Others reject this and instead take the moral values of the tale as only a general comment on the world of the pilgrims and their higher perspective (as happens in Chaucer's long romance, Troilus and Criseyde). Some critics take the Parson's Tale as ironic.

Chaucer's retraction
Chaucer's authorship has often been questioned but it is supported by manuscript evidence (it always occurs in mss where the Parson's Tale is found complete) and by a report (1434-1457) of Chaucer's death-bed repentance. The report might have been derived from the Retraction but such conversion has precedent.
Alternatives to reading the Retraction as the expression of personal remorse are to see it as an application to the Poet-narrator (the Parson's) call to penitence, as the concluding step in a poem on the theme of the pilgrimage of life, or to see is as Chaucer's use of a literary convention that includes establishing a canon of his authentic works.

Suggested resolution
Line 0 If the title or rubric: "Heere taketh the makere of this book his live" is authentic, the speaker is clearly Chaucer the poet. Chaucer the poet is the speaker for the list of books. If the title is not authentic, the lines except the list can be read as spoken by the Parson and would form the expected conventional conclusion to his treatise on penance. In the latter case, the list has to be an insertion by Chaucer or someone else. A large number of critics accept this as the case.
Line 1 "this litel tretys" could refer to the Parson's Tale but, if the Canterbury Tales is seen as a work of moral instruction, it could refer to the tales as a whole.