Many homeschool families arrive at junior or senior year realizing they never formally graded their student's work. The instruction happened, the learning was real, but grades were not assigned along the way. This is more common than you might think, and it does not mean you cannot build a legitimate transcript.
Reconstructing grades requires looking back at the work your student completed and assigning grades based on evidence. The evidence can include: completed textbook chapters and exercises, written essays and reports, test and quiz scores (if you gave any), project portfolios, standardized test results, dual enrollment grades, and your own assessment of mastery.
For courses where you have test scores or completed assignments, grading is straightforward. Add up the scores and convert to a letter grade using your chosen grading scale. For courses based on reading and discussion, evaluate whether the student demonstrated mastery of the key concepts through their participation and any written work.
If a course was completed but you truly have no basis for assigning a letter grade, you can use Pass (P) designation. Pass courses earn credit but do not affect the GPA. This is honest and accepted by colleges. Include a footnote on the transcript explaining that certain courses were completed on a pass/fail basis.
Some families combine approaches: letter grades for courses with clear assessment evidence, and Pass for courses where grading would require too much guesswork. Whatever method you choose, document your reconstruction methodology in a brief note on the transcript so admissions officers understand your approach.